class_docstr: Special keyword value.
  
  The instance of this class may be used as the default value assigned to a
  keyword if no other obvious default (e.g., `None`) is suitable,
  
  Common reasons for using this keyword are:
  
  - A new keyword is added to a function, and that function forwards its
    inputs to another function or method which can be defined outside of
    NumPy. For example, ``np.std(x)`` calls ``x.std``, so when a ``keepdims``
    keyword was added that could only be forwarded if the user explicitly
    specified ``keepdims``; downstream array libraries may not have added
    the same keyword, so adding ``x.std(..., keepdims=keepdims)``
    unconditionally could have broken previously working code.
  - A keyword is being deprecated, and a deprecation warning must only be
    emitted when the keyword is used.
code: def __new__(cls):
      # ensure that only one instance exists
      if not cls.__instance:
          cls.__instance = super().__new__(cls)
      return cls.__instance
  
file_path: numpy/numpy/_globals.py
imports: import enum
  from ._utils import set_module
label_desc: Use image node_id 1 for calling the _NoValueType obj's underlying member method code with example usage: obj.__new__(cls) and returns: cls