Creating radio meta box, need second look to make sure code is OK

I used to use Piklist to create custom meta boxes because I’m not a super developer, but now the plugin is no longer available, so I have to find another solution. Currently, I only need to radio meta box with different options that will plug into the previous plugin custom field values to keep using the feature.
I found online meta box generator, so I recreated the radio function I wanted and it seems work, but I was wondering if anyone can take a look at the code to see if it’s not missing anything:

class FormatsMetaBox{

	private $screen = array(
		'post',
        'my_article_format',        
	);

	private $meta_fields = array(
                array(
                    'label' => 'Post type picker',
                    'id' => 'my_article_format',
                    'default' => 'format-1',
                    'type' => 'radio',
                    'options' => array(
                        'format-1' => 'Standard',
                        'format-2' => 'Background',
                        'format-3' => 'Video One',
                        'format-4' => 'Video Two',
                        'format-5' => 'Review',
                        'format-6' => 'Longform',
                        'format-7' => 'Gallery',
                        'format-8' => 'Minimal',
                        'format-9' => 'Inline',
                        'format-10' => 'Affiliate',
                        'format-11' => 'Linear',
                        'format-99' => 'Legacy'
                    )
                )

	);

	public function __construct() {
		add_action( 'add_meta_boxes', array( $this, 'add_meta_boxes' ) );
		add_action( 'save_post', array( $this, 'save_fields' ) );
	}

	public function add_meta_boxes() {
		foreach ( $this->screen as $single_screen ) {
			add_meta_box(
				'Formats',
				__( 'Formats', '' ),
				array( $this, 'meta_box_callback' ),
				$single_screen,
				'side',
				'low'
			);
		}
	}

	public function meta_box_callback( $post ) {
		wp_nonce_field( 'Formats_data', 'Formats_nonce' );
		$this->field_generator( $post );
	}
	public function field_generator( $post ) {
		$output = '';
		foreach ( $this->meta_fields as $meta_field ) {
			$label = '<label for="' . $meta_field['id'] . '">' . $meta_field['label'] . '</label>';
			$meta_value = get_post_meta( $post->ID, $meta_field['id'], true );
			if ( empty( $meta_value ) ) {
				if ( isset( $meta_field['default'] ) ) {
					$meta_value = $meta_field['default'];
				}
			}
			switch ( $meta_field['type'] ) {
                        case 'radio':
                            $input = '<fieldset>';
                            $input .= '<legend class="screen-reader-text">' . $meta_field['label'] . '</legend>';
                            $i = 0;
                            foreach ( $meta_field['options'] as $key => $value ) {
                                $meta_field_value = !is_numeric( $key ) ? $key : $value;
                                $input .= sprintf(
                                    '<label><input %s id=" %s" name="%s" type="radio" value="%s"> %s</label>%s',
                                    $meta_value === $meta_field_value ? 'checked' : '',
                                    $meta_field['id'],
                                    $meta_field['id'],
                                    $meta_field_value,
                                    $value,
                                    $i < count( $meta_field['options'] ) - 1 ? '<br>' : ''
                                );
                                $i++;
                            }
                            $input .= '</fieldset>';
                            break;

				default:
                                    $input = sprintf(
                                        '<input %s id="%s" name="%s" type="%s" value="%s">',
                                        $meta_field['type'] !== 'color' ? 'style="width: 100%"' : '',
                                        $meta_field['id'],
                                        $meta_field['id'],
                                        $meta_field['type'],
                                        $meta_value
                                    );
			}
			$output .= $this->format_rows( $label, $input );
		}
		echo '<table class="form-table"><tbody>' . $output . '</tbody></table>';
	}

	public function format_rows( $label, $input ) {
		return '<tr><th style="display: inline-block">'.$label.'</th><td style="display: inline">'.$input.'</td></tr>';
	}

	public function save_fields( $post_id ) {
		if ( ! isset( $_POST['Formats_nonce'] ) )
			return $post_id;
		$nonce = $_POST['Formats_nonce'];
		if ( !wp_verify_nonce( $nonce, 'Formats_data' ) )
			return $post_id;
		if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE )
			return $post_id;
		foreach ( $this->meta_fields as $meta_field ) {
			if ( isset( $_POST[ $meta_field['id'] ] ) ) {
				switch ( $meta_field['type'] ) {
					case 'email':
						$_POST[ $meta_field['id'] ] = sanitize_email( $_POST[ $meta_field['id'] ] );
						break;
					case 'text':
						$_POST[ $meta_field['id'] ] = sanitize_text_field( $_POST[ $meta_field['id'] ] );
						break;
				}
				update_post_meta( $post_id, $meta_field['id'], $_POST[ $meta_field['id'] ] );
			} else if ( $meta_field['type'] === 'checkbox' ) {
				update_post_meta( $post_id, $meta_field['id'], '0' );
			}
		}
	}
}

if (class_exists('FormatsMetabox')) {
	new FormatsMetabox;
};