code: def __enter__(self):
      if self._nested_level == 0:
          self.activate()
      self._nested_level += 1
      # I return self, so callers can use add_builtin in a with clause.
      return self
  
file_path: catboost/contrib/python/ipython/py3/IPython/core/builtin_trap.py
imports: import builtins
  from traitlets.config.configurable import Configurable
  from traitlets import Instance
label_desc: Use image node_id 2 for calling the BuiltinTrap obj's underlying member method code with example usage: obj.__enter__() and returns: self