class_docstr: A helper for mapping categorical values to colors on demand.
code: def __call__(self, category):
      if category not in self.mapping:
          if self.colors:
              self.mapping[category] = self.colors.pop()
          else:
              raise YellowbrickValueError(
                  "Not enough colors for this many categories!"
              )
  
      return self.mapping[category]
  
file_path: yellowbrick/yellowbrick/style/colors.py
imports: import random
  import warnings
  import numpy
  import matplotlib
  import matplotlib.cm
  from copy import copy
  from yellowbrick.exceptions import YellowbrickValueError
  from distutils.version import LooseVersion
label_desc: Use image node_id 4 for calling the ColorMap obj's underlying member method code with example usage: obj.__call__(category) and returns: self