docs: def iff(self, *args, **kwargs):
          """Adds IF statements to queryset"""
          if len([x for x in kwargs.values() if x is None]):
              raise CQLEngineException("None values on iff are not allowed")
  
          clone = copy.deepcopy(self)
          for operator in args:
              if not isinstance(operator, TransactionClause):
                  raise QueryException('{} is not a valid query operator'.format(operator))
              clone._transaction.append(operator)
  
          for col_name, val in kwargs.items():
              exists = False
              try:
                  column = self.model._get_column(col_name)
              except KeyError:
                  if col_name == 'pk__token':
                      if not isinstance(val, Token):
                          raise QueryException("Virtual column 'pk__token' may only be compared to Token() values")
                      column = columns._PartitionKeysToken(self.model)
                      quote_field = False
                  else:
                      raise QueryException("Can't resolve column name: '{}'".format(col_name))
  
              if isinstance(val, Token):
                  if col_name != 'pk__token':
                      raise QueryException("Token() values may only be compared to the 'pk__token' virtual column")
                  partition_columns = column.partition_columns
                  if len(partition_columns) != len(val.value):
                      raise QueryException(
                          'Token() received {} arguments but model has {} partition keys'.format(
                              len(val.value), len(partition_columns)))
                  val.set_columns(partition_columns)
  
              if isinstance(val, BaseQueryFunction) or exists is True:
                  query_val = val
              else:
                  query_val = column.to_database(val)
  
              clone._transaction.append(TransactionClause(col_name, query_val))
  
          return clone