get_column_headers( string|WP_Screen $screen )

function get_column_headers( $screen ) {
	if ( is_string( $screen ) )
		$screen = convert_to_screen( $screen );

	static $column_headers = array();

	if ( ! isset( $column_headers[ $screen->id ] ) ) {

		/**
		 * Filters the column headers for a list table on a specific screen.
		 *
		 * The dynamic portion of the hook name, `$screen->id`, refers to the
		 * ID of a specific screen. For example, the screen ID for the Posts
		 * list table is edit-post, so the filter for that screen would be
		 * manage_edit-post_columns.
		 *
		 * @since WP-3.0.0
		 *
		 * @param array $columns An array of column headers. Default empty.
		 */
		$column_headers[ $screen->id ] = apply_filters( "manage_{$screen->id}_columns", array() );
	}

	return $column_headers[ $screen->id ];
}