Source

File: wp-includes/formatting.php

function format_to_edit( $content, $rich_text = false ) {
	/**
	 * Filters the text to be formatted for editing.
	 *
	 * @since 1.2.0
	 *
	 * @param string $content The text, prior to formatting for editing.
	 */
	$content = apply_filters( 'format_to_edit', $content );
	if ( ! $rich_text ) {
		$content = esc_textarea( $content );
	}
	return $content;
}