meta option

array(
            'name'      => 'option',
            'type'      => 'select',
            'label'     => __( 'Option', 'attachments' ),
            'meta'      => array(
                'allow_null'    => false,
                'multiple'      => true,
                'options'       => 'my_selector_function',
            ),
        )

function my_selector_function(){
    //$categories = get_terms( 'portfolio_texonomy', 'orderby=count&hide_empty=0&fields=names' );
    global $wpdb;
    $taxonomies = array(
        'portfolio_texonomy'
    );
    $args = array(
        'orderby'           => 'name',
        'order'             => 'ASC',
        'hide_empty'        => 0,
        'exclude'           => array(),
        'exclude_tree'      => array(),
        'include'           => array(),
        'number'            => '',
        'fields'            => 'all',
        'slug'              => '',
        'parent'            => '',
        'hierarchical'      => true,
        'child_of'          => 0,
        'childless'         => false,
        'get'               => '',
        'name__like'        => '',
        'description__like' => '',
        'pad_counts'        => false,
        'offset'            => '',
        'search'            => '',
        'cache_domain'      => 'core'
    );

    $terms = get_terms($taxonomies, $args);

    $_posts = array();

    foreach($terms as $p){

        $_posts[$p->term_id] = $p->name;
    }
    return $_posts;

}