protected function _getListFieldsNullVal() {
		$result = [];
		$schema = $this->schema();
		$data = array_filter(
			$schema,
			function ($v, $k) {

				return isset($v['null']) && $v['null'] === true;
			},
			ARRAY_FILTER_USE_BOTH
		);
		if (!empty($data)) {
			$result = array_keys($data);
		}

		return $result;
	}
protected function _getListFieldsNullVal() {
		$result = [];
		$schema = $this->schema();
		$data = array_filter(
			$schema,
			function ($v, $k) {

				return isset($v['null']) && $v['null'] === true;
			},
			ARRAY_FILTER_USE_BOTH
		);
		if (!empty($data)) {
			$result = array_keys($data);
		}

		return $result;
	}
protected function _getListFieldsNullVal ( ) { $ result = [ ] ; $ schema = $ this -> schema ( ) ; $ data = array_filter ( $ schema , function ( $ v , $ k ) { return isset ( $ v [ 'null' ] ) && $ v [ 'null' ] === true ; } , ARRAY_FILTER_USE_BOTH ) ; if ( ! empty ( $ data ) ) { $ result = array_keys ( $ data ) ; } return $ result ; }
Return list of fields with allowed null value

@return array Return list of fields.
Return list of fields with allowed null value