Source

File: wp-includes/class-wp-theme.php

public function get_page_templates( $post = null, $post_type = 'page' ) {
		if ( $post ) {
			$post_type = get_post_type( $post );
		}

		$post_templates = $this->get_post_templates();
		$post_templates = isset( $post_templates[ $post_type ] ) ? $post_templates[ $post_type ] : array();

		/**
		 * Filters list of page templates for a theme.
		 *
		 * @since 4.9.6
		 *
		 * @param string[]     $post_templates Array of template header names keyed by the template file name.
		 * @param WP_Theme     $this           The theme object.
		 * @param WP_Post|null $post           The post being edited, provided for context, or null.
		 * @param string       $post_type      Post type to get the templates for.
		 */
		$post_templates = (array) apply_filters( 'theme_templates', $post_templates, $this, $post, $post_type );

		/**
		 * Filters list of page templates for a theme.
		 *
		 * The dynamic portion of the hook name, `$post_type`, refers to the post type.
		 *
		 * @since 3.9.0
		 * @since 4.4.0 Converted to allow complete control over the `$page_templates` array.
		 * @since 4.7.0 Added the `$post_type` parameter.
		 *
		 * @param string[]     $post_templates Array of template header names keyed by the template file name.
		 * @param WP_Theme     $this           The theme object.
		 * @param WP_Post|null $post           The post being edited, provided for context, or null.
		 * @param string       $post_type      Post type to get the templates for.
		 */
		$post_templates = (array) apply_filters( "theme_{$post_type}_templates", $post_templates, $this, $post, $post_type );

		return $post_templates;
	}