code: def _register_builtin_message_func():
      """Register builtin message functions"""
      target = ["u", "v", "e"]
      for lhs, rhs in product(target, target):
          if lhs != rhs:
              for binary_op in ["add", "sub", "mul", "div", "dot"]:
                  func = _gen_message_builtin(lhs, rhs, binary_op)
                  setattr(sys.modules[__name__], func.__name__, func)
                  __all__.append(func.__name__)
  
file_path: dgl/python/dgl/function/message.py
imports: from __future__ import absolute_import
  import sys
  from itertools import product
  from .base import BuiltinFunction, TargetCode
label_desc: Use image node_id 4 for calling a global function with example usage: _register_builtin_message_func() without return types