code: def add_string(self, s: bytes):
      s = s + b"\x00"
      self.pack_string += str(len(s)) + "s"
      self.pack_args.append(s)
      return self.add_length(len(s))
  
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 8 for calling the PostgresPacketBuilder obj's underlying member method code with example usage: obj.add_string(s) and returns: self