code: def write_gps_datum(self, code=None, gps_datum=None):
          
  
          if code is None:
              code = 100
  
          if gps_datum is None:
              gps_datum = 'WGS-1984'
  
          self.write_fr_header(
              'DTM',
              '%03d' % code,
              subtype_long='GPSDATUM',
              value_long=gps_datum,
          )
docs: Write the mandatory GPS datum header::
  
              writer.write_gps_datum()
              # -> HFDTM100GPSDATUM:WGS-1984
  
              writer.write_gps_datum(33, 'Guam-1963')
              # -> HFDTM033GPSDATUM:Guam-1963
  
          Note that the default GPS datum is WGS-1984 and you should use that
          unless you have very good reasons against it.
  
          :param code: the GPS datum code as defined in the IGC file
              specification, section A8
          :param gps_datum: the GPS datum in written form