docs: def valueFromDataset(cls, datatype, value, metadata=None, tmap=None):
          """
            Return the value contained by dataset argument, after casting to
            correct type and performing type-specific validation
          """
          if tmap is None:
              tmap = typemap
          obj = cls.fromDataset(datatype, value, metadata=metadata, tmap=tmap)
          return obj.value