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 __call__(self, inline, inline_spacing=5, n=-1, timeout=-1):
      self.inline = inline
      self.inline_spacing = inline_spacing
  
      BlockingMouseInput.__call__(
          self, n=n, timeout=timeout, show_clicks=False
      )
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import six
  import matplotlib.lines
  import logging
label_desc: Use image node_id 6 for calling the BlockingContourLabeler obj's underlying member method code with example usage: obj.__call__(inline, inline_spacing, n, timeout) without return types