code: def _preprocess_params(cls, kwargs):
          
          # kwargs.pop('csrf_token', None)
          for attr, val in kwargs.items():
              if cls.is_the_primary_key(attr) and cls._prevent_primary_key_initialization_:
                  del kwargs[attr]
                  continue
              if val == "":
                  # Making an assumption that there is no good usecase
                  # for setting an empty string. This will help prevent
                  # cases where empty string is sent because of client
                  # not clearing form fields to null
                  kwargs[attr] = None
                  continue
              if attr in class_mapper(cls).relationships and attr not in cls._no_overwrite_:
                  rel = class_mapper(cls).relationships[attr]
                  if rel.uselist:
                      if isinstance(val, list):
                          if all(isinstance(v, dict) for v in val):
                              rel_cls = cls.mapped_rel_class(attr)
                              kwargs[attr] = rel_cls.update_or_new_all(
                                  list_of_kwargs=val, keys=[rel_cls.primary_key_name()])
                      elif isinstance(val, dict):
                          rel_cls = cls.mapped_rel_class(attr)
                          mapping_col = rel.collection_class().keyfunc.name
                          list_of_kwargs = [merge(v, {mapping_col: k}) for k, v in val.items()]
                          kwargs[attr] = {getattr(obj, mapping_col): obj for obj in rel_cls.update_or_new_all(
                              list_of_kwargs=list_of_kwargs, keys=[rel_cls.primary_key_name()])}
                  elif isinstance(val, dict):
                      rel_cls = cls.mapped_rel_class(attr)
                      kwargs[attr] = rel_cls.update_or_new(
                          **merge(val, {'keys': [rel_cls.primary_key_name()]}))
          return kwargs
docs: Returns a preprocessed dictionary of parameters.
          Use this to filter the kwargs passed to `new`, `create`,
          `build` methods.
  
          Args:
  
              **kwargs: a dictionary of parameters