class_docstr: provide attribute-style access to a nested dict
class_docstr_tok: ["provide","attribute-style","access","to","a","nested","dict"]
code: def __setattr__(self, key, val):
      prefix = object.__getattribute__(self, "prefix")
      if prefix:
          prefix += "."
      prefix += key
      # you can't set new keys
      # can you can't overwrite subtrees
      if key in self.d and not isinstance(self.d[key], dict):
          _set_option(prefix, val)
      else:
          raise OptionError(
              "You can only set the value of existing options"
          )
  
imports: from collections import namedtuple
  from contextlib import contextmanager
  import re
  import warnings
  import pandas.compat
  from pandas.compat import lmap, map, u
label_desc: Use image node_id 2 for calling the DictWrapper obj's underlying member method code with example usage: obj.__setattr__(key, val) without return types