amp_is_request example

$prefix = 'ak_';

        // Contact Form 7 uses _wpcf7 as a prefix to know which fields to exclude from comment_content.         if ( 'wpcf7_form_elements' === current_filter() ) {
            $prefix = '_wpcf7_ak_';
        }

        $fields .= '<p style="display: none !important;">';
        $fields .= '<label>&#916;<textarea name="' . $prefix . 'hp_textarea" cols="45" rows="8" maxlength="100"></textarea></label>';

        if ( ! function_exists( 'amp_is_request' ) || ! amp_is_request() ) {
            // Keep track of how many ak_js fields are in this page so that we don't re-use             // the same ID.             static $field_count = 0;

            $field_count++;

            $fields .= '<input type="hidden" id="ak_js_' . $field_count . '" name="' . $prefix . 'js" value="' . mt_rand( 0, 250 ) . '"/>';
            $fields .= '<script>document.getElementById( "ak_js_' . $field_count . '" ).setAttribute( "value", ( new Date() ).getTime() );</script>';
        }

        $fields .= '</p>';