code: def unregister_cmap(name):
      """
      Remove a colormap recognized by :func:`get_cmap`.
  
      You may not remove built-in colormaps.
  
      If the named colormap is not registered, returns with no error, raises
      if you try to de-register a default colormap.
  
      .. warning::
  
        Colormap names are currently a shared namespace that may be used
        by multiple packages. Use `unregister_cmap` only if you know you
        have registered that name before. In particular, do not
        unregister just in case to clean the name before registering a
        new colormap.
  
      Parameters
      ----------
      name : str
          The name of the colormap to be un-registered
  
      Returns
      -------
      ColorMap or None
          If the colormap was registered, return it if not return `None`
  
      Raises
      ------
      ValueError
         If you try to de-register a default built-in colormap.
      """
      cmap = _colormaps.get(name, None)
      _colormaps.unregister(name)
      return cmap
  
imports: from collections.abc import Mapping
  import functools
  import numpy
  from numpy import ma
  import matplotlib
  from matplotlib import _api, colors, cbook, scale
  from matplotlib._cm import datad
  from matplotlib._cm_listed import cmaps
label_desc: Use image node_id 4 for calling a global function with example usage: unregister_cmap(name) and returns: cmap