private function maybe_do_post_thumbnail( $field, $post ) {
		if ( 'post_thumbnail' == $field || false !== strpos( $field, 'post_thumbnail.' ) ) {
			$size = 'thumbnail';
			if ( false !== ( $pos = strpos( $field, '.' ) ) ) {
				$size = substr( $field, $pos + 1);
			}

			$id = get_post_thumbnail_id( $post->ID );
			if ( 0 < absint( $id ) ) {
				$img = wp_get_attachment_image_src( $id, $size);
				if ( is_array( $img ) ) {
					return $img[0];

				}

			}

			return 0;

		}

		return false;



	}