class_docstr: Tag scope object to set tag for operators, working as context
  manager and decorator both. See also tag_scope.
code: def __enter__(self):
      if TagScope._current is not None:
          raise ValueError("nested op_tag is not allowed for now")
      self._old_scope = TagScope._current
      TagScope._current = self
      return self
  
file_path: tvm/python/tvm/te/tag.py
imports: import warnings
  from tvm._ffi.base import decorate
label_desc: Use image node_id 3 for calling the TagScope obj's underlying member method code with example usage: obj.__enter__() and returns: self