code: def _register_builtin_reduce_func():
      """Register builtin reduce functions"""
      for reduce_op in ["max", "min", "sum", "mean"]:
          builtin = _gen_reduce_builtin(reduce_op)
          setattr(sys.modules[__name__], reduce_op, builtin)
          __all__.append(reduce_op)
  
file_path: dgl/python/dgl/function/reducer.py
imports: from __future__ import absolute_import
  import sys
  from .base import BuiltinFunction
label_desc: Use image node_id 2 for calling a global function with example usage: _register_builtin_reduce_func() without return types