class_docstr: Class that creates a callable object to retrieve mouse clicks in a
  blocking way.
  
  This class will also retrieve keyboard clicks and treat them like
  appropriate mouse clicks (delete and backspace are like mouse button 3,
  enter is like mouse button 2 and all others are like mouse button 1).
code: def __init__(self, fig, mouse_add=1, mouse_pop=3, mouse_stop=2):
      BlockingInput.__init__(
          self,
          fig=fig,
          eventslist=("button_press_event", "key_press_event"),
      )
      self.button_add = mouse_add
      self.button_pop = mouse_pop
      self.button_stop = mouse_stop
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import six
  import matplotlib.lines
  import logging
label_desc: Use image node_id 1 to create a new BlockingMouseInput object from inherited base classes: BlockingInput with example: obj = BlockingMouseInput(fig, mouse_add, mouse_pop, mouse_stop)