code: def prepare(cls, value, length=0, position=0, is_last_data=True):
          
          hstruct = WriteLobHeader.header_struct
          lob_option_dataincluded = WriteLobHeader.LOB_OPTION_DATAINCLUDED if length > 0 else 0
          lob_option_lastdata = WriteLobHeader.LOB_OPTION_LASTDATA if is_last_data else 0
          options = lob_option_dataincluded | lob_option_lastdata
          pfield = hstruct.pack(cls.type_code, options, length, position)
          return pfield
docs: Prepare Lob header.
          Note that the actual lob data is NOT written here but appended after the parameter block for each row!