public function field($field=null) {
		$default_render = $this->default_render;
		if($default_render !== null)
			return $default_render($field);
		elseif($field instanceof Field)
			return $field->def();
	}
public function field($field=null) {
		$default_render = $this->default_render;
		if($default_render !== null)
			return $default_render($field);
		elseif($field instanceof Field)
			return $field->def();
	}
public function field ( $ field = null ) { $ default_render = $ this -> default_render ; if ( $ default_render !== null ) return $ default_render ( $ field ) ; elseif ( $ field instanceof Field ) return $ field -> def ( ) ; }
Render a field or a sub-group.
@param  Group|Field $field
@return string|Widget
Render a field or a sub - group .