class_docstr: Dictionary with support for nans.
code: def __missing__(self, key):
      if hasattr(self, "nan_value") and is_scalar_nan(key):
          return self.nan_value
      raise KeyError(key)
  
imports: from collections import Counter
  from contextlib import suppress
  from typing import NamedTuple
  import numpy
  from .None import is_scalar_nan
label_desc: Use image node_id 2 for calling the _nandict obj's underlying member method code with example usage: obj.__missing__(key) and returns: self