code: def add_record_check(self, record_check, modulus=1):
          
  
          assert callable(record_check), 'record check must be a callable function'
  
          t = record_check, modulus
          self._record_checks.append(t)
docs: Add a record check function.
  
          Arguments
          ---------
  
          `record_check` - a function that accepts a single argument (a record as
          a dictionary of values indexed by field name) and raises a
          `RecordError` if the record is not valid
  
          `modulus` - apply the check to every nth record, defaults to 1 (check
          every record)