code: def write(self, write_file: BinaryIO):
      if len(self.identifier) == 0:
          raise Exception("Can't write without identifier.")
      pack = "!c"
  
      # Send length
      # Ensures 'i' in pack and self.length in 2nd position of respective variables.
      # Also adds 4 to length to include int32 rep of length
      self.length += 4
      pack += "i"
      self.pack_args = [self.length] + self.pack_args
  
      pack += self.pack_string
      self.logger.debug("writing:")
      self.logger.debug("pack string: %s" % self.pack_string)
      self.logger.debug("identifier: %s" % self.pack_string)
      self.logger.debug("pack args:")
      for arg in self.pack_args:
          self.logger.debug("arg: %s" % str(arg))
      packed_binary = struct.pack(
          pack, self.identifier, *self.pack_args
      )
      write_file.write(packed_binary)
  
imports: import struct
  from typing import List, Any, BinaryIO, Sequence, Dict
  from mindsdb.api.postgres.postgres_proxy.utilities import strip_null_byte
  from mindsdb.utilities import log
  import time
  from mindsdb.api.postgres.postgres_proxy.postgres_packets.postgres_fields import PostgresField
  from mindsdb.api.postgres.postgres_proxy.postgres_packets.postgres_message_identifiers import PostgresBackendMessageIdentifier, PostgresFrontendMessageIdentifier, PostgresAuthType
label_desc: Use image node_id 6 for calling the PostgresPacketBuilder obj's underlying member method code with example usage: obj.write(write_file) without return types