_key = false;
			foreach ( $data as $key => $schema ) {
				if ( $key === $insert_in ) {
					$insert_key = $key;
					break;
				}

				if ( ! isset( $schema['@type'] ) ) {
					continue;
				}

				if ( $schema['@type'] === $insert_in ) {
					$insert_key = $key;
					break;
				}
			}
			if ( ! $insert_key ) {
				continue;
			}

			// Now insert the schema(s).
			foreach ( $schemas as $schema ) {
				$schema_key  = $schema['key'];
				$schema_data = $schema['schema'];

				unset( $schema_data['isPrimary'], $schema_data['isCustom'], $schema_data['isTemplate'], $schema_data['metadata'] );

				$schema_data = $jsonld->replace_variables( $schema_data );

				foreach ( $schema_data as $key => $value ) {
					if ( ! isset( $data[ $insert_key ][ $key ] ) ) {
						$data[ $insert_key ][ $key ] = $value;	
					}
				}
			}
		}

		return $data;
	}

	/**
	 * Add About & Mention attributes to Webpage schema.
	 *
	 * @param  array $data Array of json-ld data.
	 * @return array
	 */
	public function add_about_mention_attributes( $data ) {
		if ( ! is_singular() || empty( $data['WebPage'] ) ) {
			return $data;
		}

		global $post;
		if ( ! $post->post_content ) {
			return $data;
		}

		preg_match_all( '|<a[^>]+>([^<]+)</a>|', $post->post_content, $matches );
		if ( empty( $matches ) || empty( $matches[0] ) ) {
			return $data;
		}

		foreach ( $matches[0] as $link ) {
			$attrs = HTML::extract_attributes( $link );
			if ( empty( $attrs['data-schema-attribute'] ) ) {
				continue;
			}

			$attributes = explode( ' ', $attrs['data-schema-attribute'] );
			if ( in_array( 'about', $attributes, true ) ) {
				$data['WebPage']['about'][] = [
					'@type'  => 'Thing',
					'name'   => wp_strip_all_tags( $link ),
					'sameAs' => $attrs['href'],
				];
			}

			if ( in_array( 'mentions', $attributes, true ) ) {
				$data['WebPage']['mentions'][] = [
					'@type'  => 'Thing',
					'name'   => wp_strip_all_tags( $link ),
					'sameAs' => $attrs['href'],
				];
			}
		}

		return $data;
	}

	/**
	 * Filter to change the itemList schema data.
	 *
	 * @param array $schema Snippet Data.
	 * @return array
	 */
	public function filter_item_list_schema( $schema ) {
		if ( ! is_archive() ) {
			return $schema;
		}

		$elements = [];
		$count    = 1;
		while ( have_posts() ) {
			the_post();
			$elements[] = [
				'@type'    => 'ListItem',
				'position' => $count,
				'url'      => get_the_permalink(),
			];

			$count++;
		}

		wp_reset_postdata();

		$schema['itemListElement'] = $elements;

		return $schema;
	}

	/**
	 * Validate Schema Data.
	 *
	 * @param array $schemas Array of json-ld data.
	 *
	 * @return array
	 */
	public function validate_schema_data( $schemas ) {
		if ( empty( $schemas ) ) {
			return $schemas;
		}

		$validate_types = [ 'Dataset', 'LocalBusiness' ];
		foreach ( $schemas as $id => $schema ) {
			$type = isset( $schema['@type'] ) ? $schema['@type'] : '';
			if ( ! Str::starts_with( 'schema-', $id ) || ! in_array( $type, $validate_types, true ) ) {
				continue;
			}

			$hash = [
				'isPartOf'   => true,
				'publisher'  => 'LocalBusiness' === $type,
				'inLanguage' => 'LocalBusiness' === $type,
			];

			foreach ( $hash as $property => $value ) {
				if ( ! $value || ! isset( $schema[ $property ] ) ) {
					continue;
				}

				if ( 'Dataset' === $type && 'isPartOf' === $property && ! empty( $schema[ $property ]['@type'] ) ) {
					continue;
				}

				unset( $schemas[ $id ][ $property ] );
			}

			if ( 'Dataset' === $type && ! empty( $schema['publisher'] ) ) {
				$schemas[ $id ]['creator'] = $schema['publisher'];
				unset( $schemas[ $id ]['publisher'] );
			}
		}

		return $schemas;
	}

	/**
	 * Get Schema data from Schema Templates post type.
	 *
	 * @param array  $data   Array of json-ld data.
	 * @param JsonLD $jsonld Instance of jsonld.
	 *
	 * @return array
	 */
	public function add_schema_from_shortcode( $data, $jsonld ) {
		if ( ! is_singular() || ! $this->do_filter( 'rank_math/schema/add_shortcode_schema', true ) ) {
			return $data;
		}

		global $post;
		$blocks = parse_blocks( $post->post_content );
		if ( ! empty( $blocks ) ) {
			foreach ( $blocks as $block ) {
				if ( 'rank-math/rich-snippet' !== $block['blockName'] ) {
					continue;
				}

				$id      = isset( $block['attrs']['id'] ) ? $block['attrs']['id'] : '';
				$post_id = isset( $block['attrs']['post_id'] ) ? $block['attrs']['post_id'] : '';

				if ( ! $id && ! $post_id ) {
					continue;
				}

				$data = array_merge( $data, $this->get_schema_data_by_id( $id, $post_id, $jsonld, $data ) );
			}
		}

		$regex = '/\[rank_math_rich_snippet (.*)\]/m';
		preg_match_all( $regex, $post->post_content, $matches, PREG_SET_ORDER, 0 );
		if ( ! empty( $matches ) ) {
			foreach ( $matches as $key => $match ) {
				parse_str( str_replace( ' ', '&', $match[1] ), $output );

				$post_id = isset( $output['post_id'] ) ? str_replace( [ '"', "'" ], '', $output['post_id'] ) : '';
				$id      = isset( $output['id'] ) ? str_replace( [ '"', "'" ], '', $output['id'] ) : '';
				$data    = array_merge( $data, $this->get_schema_data_by_id( $id, $post_id, $jsonld, $data ) );
			}
		}

		return $data;
	}

	/**
	 * Add Manufacturer property to Product schema.
	 *
	 * @param array $schema Product schema data.
	 * @return array
	 */
	public function add_manufacturer_property( $schema ) {
		if ( empty( $schema['manufacturer'] ) ) {
			return $schema;
		}

		$type = Helper::get_settings( 'titles.knowledgegraph_type' );
		$type = 'company' === $type ? 'organization' : 'person';

		$schema['manufacturer'] = [ '@id' => home_url( "/#{$type}" ) ];
		return $schema;
	}

	/**
	 * Remove empty offers data from the Product schema.
	 *
	 * @param array $schema Product schema data.
	 * @return array
	 */
	public function remove_empty_offers( $schema ) {
		if (
			empty( $schema['offers'] ) ||
			empty( $schema['review'] ) ||
			(
				empty( $schema['review']['positiveNotes'] ) &&
				empty( $schema['review']['negativeNotes'] )
			)
		) {
			return $schema;
		}

		if ( ! empty( $schema['offers']['price'] ) ) {
			return $schema;
		}

		unset( $schema['offers'] );

		return $schema;
	}

	/**
	 * Backward compatibility code to move the positiveNotes & negativeNotes properties in review.
	 *
	 * @param array $schema Schema data.
	 * @return array
	 *
	 * @since 3.0.19
	 */
	public function schema_entity( $schema ) {
		if ( empty( $schema['review'] ) ) {
			return $schema;
		}

		if ( ! empty( $schema['positiveNotes'] ) ) {
			$schema['review']['positiveNotes'] = $schema['positiveNotes'];
			unset( $schema['positiveNotes'] );
		}

		if ( ! empty( $schema['negativeNotes'] ) ) {
			$schema['review']['negativeNotes'] = $schema['negativeNotes'];
			unset( $schema['negativeNotes'] );
		}

		return $schema;
	}

	/**
	 * Convert isFamilyFriendly property used in Video schema to boolean.
	 *
	 * @param array $schema Video schema data.
	 * @return array
	 *
	 * @since 2.13.0
	 */
	public function convert_familyfriendly_property( $schema ) {
		if ( empty( $schema['isFamilyFriendly'] ) ) {
			return $schema;
		}

		$schema['isFamilyFriendly'] = 'True';
		return $schema;
	}

	/**
	 * Get Schema data by ID.
	 *
	 * @param string $id   Schema shortcode ID.
	 * @param int    $post_id Post ID.
	 * @param JsonLD $jsonld Instance of jsonld.
	 * @param array  $data   Array of json-ld data.
	 *
	 * @return array
	 */
	private function get_schema_data_by_id( $id, $post_id, $jsonld, $data ) {
		$schemas         = $id ? DB::get_schema_by_shortcode_id( trim( $id ) ) : DB::get_schemas( trim( $post_id ) );
		$current_post_id = get_the_ID();
		if (
			empty( $schemas ) ||
			(
				isset( $schemas['post_id'] ) && $current_post_id === (int) $schemas['post_id']
			) ||
			$post_id === $current_post_id
		) {
			return [];
		}

		$post_id = isset( $schemas['post_id'] ) ? $schemas['post_id'] : $post_id;
		$schemas = isset( $schemas['schema'] ) ? [ $schemas['schema'] ] : $schemas;
		$schemas = $jsonld->replace_variables( $schemas, get_post( $post_id ) );
		$schemas = $jsonld->filter( $schemas, $jsonld, $data );

		if ( isset( $schemas[0]['isPrimary'] ) ) {
			unset( $schemas[0]['isPrimary'] );
		}

		return $schemas;
	}
}
<br />
<b>Fatal error</b>:  Uncaught Error: Class 'RankMathPro\Schema\Frontend' not found in /home/candoodesigncom/public_html/wp-content/plugins/seo-by-rank-math-pro/includes/modules/schema/class-schema.php:42
Stack trace:
#0 /home/candoodesigncom/public_html/wp-content/plugins/seo-by-rank-math-pro/includes/modules/schema/class-schema.php(30): RankMathPro\Schema\Schema-&gt;includes()
#1 /home/candoodesigncom/public_html/wp-content/plugins/seo-by-rank-math/includes/module/class-manager.php(487): RankMathPro\Schema\Schema-&gt;__construct()
#2 /home/candoodesigncom/public_html/wp-content/plugins/seo-by-rank-math/includes/module/class-manager.php(467): RankMath\Module\Manager-&gt;load_module('rich-snippet', Object(RankMath\Module\Module))
#3 /home/candoodesigncom/public_html/wp-includes/class-wp-hook.php(324): RankMath\Module\Manager-&gt;load_modules('')
#4 /home/candoodesigncom/public_html/wp-includes/class-wp-hook.php(348): WP_Hook-&gt;apply_filters(NULL, Array)
#5 /home/candoodesigncom/public_html/wp-includes/plugin.php(517): WP_Hook-&gt;do_action(Array) in <b>/home/candoodesigncom/public_html/wp-content/plugins/seo-by-rank-math-pro/includes/modules/schema/class-schema.php</b> on line <b>42</b><br />