public function generate_multiselect_html( $key, $data ) {
		$field_key = $this->get_field_key( $key );
		$defaults  = array(
			'title'             => '',
			'disabled'          => false,
			'class'             => '',
			'css'               => '',
			'placeholder'       => '',
			'type'              => 'text',
			'desc_tip'          => false,
			'description'       => '',
			'custom_attributes' => array(),
			'select_buttons'    => false,
			'options'           => array(),
		);

		$data  = wp_parse_args( $data, $defaults );
		$value = (array) $this->get_option( $key, array() );

		ob_start();
		?>
		<tr valign="top">
			<th scope="row" class="titledesc">
				<label for="<?php echo esc_attr( $field_key ); ?>"><?php echo wp_kses_post( $data['title'] ); ?> <?php echo $this->get_tooltip_html( $data ); // WPCS: XSS ok. ?></label>
			</th>
			<td class="forminp">
				<fieldset>
					<legend class="screen-reader-text"><span><?php echo wp_kses_post( $data['title'] ); ?></span></legend>
					<select multiple="multiple" class="multiselect <?php echo esc_attr( $data['class'] ); ?>" name="<?php echo esc_attr( $field_key ); ?>[]" id="<?php echo esc_attr( $field_key ); ?>" style="<?php echo esc_attr( $data['css'] ); ?>" <?php disabled( $data['disabled'], true ); ?> <?php echo $this->get_custom_attribute_html( $data ); // WPCS: XSS ok. ?>>
						<?php foreach ( (array) $data['options'] as $option_key => $option_value ) : ?>
							<?php if ( is_array( $option_value ) ) : ?>
								<optgroup label="<?php echo esc_attr( $option_key ); ?>">
									<?php foreach ( $option_value as $option_key_inner => $option_value_inner ) : ?>
										<option value="<?php echo esc_attr( $option_key_inner ); ?>" <?php selected( in_array( (string) $option_key_inner, $value, true ), true ); ?>><?php echo esc_html( $option_value_inner ); ?></option>
									<?php endforeach; ?>
								</optgroup>
							<?php else : ?>
								<option value="<?php echo esc_attr( $option_key ); ?>" <?php selected( in_array( (string) $option_key, $value, true ), true ); ?>><?php echo esc_html( $option_value ); ?></option>
							<?php endif; ?>
						<?php endforeach; ?>
					</select>
					<?php echo $this->get_description_html( $data ); // WPCS: XSS ok. ?>
					<?php if ( $data['select_buttons'] ) : ?>
						<br/><a class="select_all button" href="#"><?php esc_html_e( 'Select all', 'woocommerce' ); ?></a> <a class="select_none button" href="#"><?php esc_html_e( 'Select none', 'woocommerce' ); ?></a>
					<?php endif; ?>
				</fieldset>
			</td>
		</tr>
		<?php

		return ob_get_clean();
	}