code: def set_units(self, unit):
          
          self._units = validate_type(unit, type(None), *six.string_types)
docs: Set the unit for this data point
  
          Unit, as with data_type, are actually associated with the stream and not
          the individual data point.  As such, changing this within a stream is
          not encouraged.  Setting the unit on the data point is useful when the
          stream might be created with the write of a data point.