code: def _postprocess_data(self, data):
          
          new_data = {}
          for k, values in data.items():
              values = decode_bytes(values) # Bytes need decoding to strings
  
              # Certain datetime types need to be converted
              if len(values) and isinstance(values[0], cftime_types):
                  if any(v.calendar not in _STANDARD_CALENDARS for v in values):
                      self.param.warning(
                          'Converting cftime.datetime from a non-standard '
                          'calendar (%s) to a standard calendar for plotting. '
                          'This may lead to subtle errors in formatting '
                          'dates, for accurate tick formatting switch to '
                          'the matplotlib backend.' % values[0].calendar)
                  values = cftime_to_timestamp(values, 'ms')
              new_data[k] = values
          return new_data
docs: Applies necessary type transformation to the data before
          it is set on a ColumnDataSource.