init func as lazy functon instance

        Args:
            function_meta (dict): function meta including name, args and kwargs

def __parse(self, function_meta):
        """ init func as lazy functon instance

        Args:
            function_meta (dict): function meta including name, args and kwargs
        """
        self._func = get_mapping_function(
            function_meta["func_name"],
            self.functions_mapping
        )
        self.func_name = self._func.__name__
        self._args = prepare_lazy_data(
            function_meta.get("args", []),
            self.functions_mapping,
            self.check_variables_set
        )
        self._kwargs = prepare_lazy_data(
            function_meta.get("kwargs", {}),
            self.functions_mapping,
            self.check_variables_set
        )

        if self.func_name == "load_csv_file":
            if len(self._args) != 1 or self._kwargs:
                raise exceptions.ParamsError("P() should only pass in one argument!")
            self._args = [self._args[0]]
        elif self.func_name == "get_os_environ":
            if len(self._args) != 1 or self._kwargs:
                raise exceptions.ParamsError("ENV() should only pass in one argument!")
            self._args = [self._args[0]]