code: def __parse(self, function_meta):
          
          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]]
docs: init func as lazy functon instance
  
          Args:
              function_meta (dict): function meta including name, args and kwargs