code: def BytesByteSize(field_number, b):
      return (
          TagByteSize(field_number)
          + _VarUInt64ByteSizeNoTag(len(b))
          + len(b)
      )
  
imports: import struct
  from google.protobuf import descriptor
  from google.protobuf import message
label_desc: Use image node_id 21 for calling a global function with example usage: BytesByteSize(field_number, b) and returns: unknown