private function get_parameters( $spec = array() ) {
		$local_parameters  = array_column( $spec, 'name' );
		$global_parameters = array_column(
			WP_CLI\SynopsisParser::parse( $this->get_global_params() ),
			'name'
		);

		return array_unique( array_merge( $local_parameters, $global_parameters ) );
	}