class_docstr: Class that creates a callable object that uses mouse clicks or key
  clicks on a figure window to place contour labels.
code: def add_click(self, event):
      self.button1(event)
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import six
  import matplotlib.lines
  import logging
label_desc: Use image node_id 2 for calling the BlockingContourLabeler obj's underlying member method code with example usage: obj.add_click(event) without return types