class_docstr: This class implements a dummy wrapper to fix a bug in the Python
  standard library for string formatting.
  
  See https://bugs.python.org/issue13598 for information about why
  this is necessary.
code: def __len__(self):
      return len(self._kwargs)
  
imports: import operator
  import types
  import warnings
  from collections import deque
  from string import Formatter
  from markupsafe import EscapeFormatter
  from markupsafe import Markup
  from ._compat import abc
  from ._compat import PY2
  from ._compat import range_type
  from ._compat import string_types
  from .environment import Environment
  from .exceptions import SecurityError
label_desc: Use image node_id 4 for calling the _MagicFormatMapping obj's underlying member method code with example usage: obj.__len__() and returns: len