docs: def is_valid(self):
          """Tests if ths form is in a valid state for submission.
  
          A form is valid if all required data has been supplied compliant
          with any constraints.
  
          return: (boolean) - false if there is a known error in this
                  form, true otherwise
          raise:  OperationFailed - attempt to perform validation failed
          compliance: mandatory - This method must be implemented.
  
          """
          validity = True
          for element in self._validity_map:
              if self._validity_map[element] is not VALID:
                  validity = False
          return validity