code: def init_group_write(self, dst_addr=1, data=None, dptsize=0):
          
          self.init_group(dst_addr)
  
          # unnumbered data packet, group write
          self.tpci_apci = 0x00 * 256 + 0x80
  
          self.dptsize = dptsize
          if data is None:
              self.data = [0]
          else:
              self.data = data
docs: Initialize the CEMI frame for a group write operation.