old_contents: """
  Interactor
  
  This class can be used to simply managing callback resources.
  Callbacks are often used by interactors with vtk and callbacks
  are hard to keep track of.
  Use multiple inheritance to inherit from this class to get access
  to the convenience methods.
  
  Observers for vtk events can be added through 
  AddObserver(obj, eventName, callbackFunction) and when it is time 
  to clean up, just call cleanUpCallbacks().
  
  :Authors:
  	Berend Klein Haneveld
  """
  
  
  class Interactor(object):
  	"""
  	Interactor
  	"""
  
  	def __init__(self):
  		super(Interactor, self).__init__()
  
  	def AddObserver(self, obj, eventName, callbackFunction):
  		"""
  		Creates a callback and stores the callback so that later
  		on the callbacks can be properly cleaned up.
  		"""
  		if not hasattr(self, "_callbacks"):
  			self._callbacks = []
  
  		callback = obj.AddObserver(eventName, callbackFunction)
  		self._callbacks.append((obj, callback))
  
  	def cleanUpCallbacks(self):
  		"""
  		Cleans up the vtkCallBacks
  		"""
  		if not hasattr(self, "_callbacks"):
  			return
  
  		for obj, callback in self._callbacks:
  			obj.RemoveObserver(callback)
  		self._callbacks = []
  
new_contents: """
  Interactor
  
  This class can be used to simply managing callback resources.
  Callbacks are often used by interactors with vtk and callbacks
  are hard to keep track of.
  Use multiple inheritance to inherit from this class to get access
  to the convenience methods.
  
  Observers for vtk events can be added through
  AddObserver(obj, eventName, callbackFunction) and when it is time
  to clean up, just call cleanUpCallbacks().
  
  :Authors:
  	Berend Klein Haneveld
  """
  
  
  class Interactor(object):
  	"""
  	Interactor
  	"""
  
  	def __init__(self):
  		super(Interactor, self).__init__()
  
  	def AddObserver(self, obj, eventName, callbackFunction):
  		"""
  		Creates a callback and stores the callback so that later
  		on the callbacks can be properly cleaned up.
  		"""
  		if not hasattr(self, "_callbacks"):
  			self._callbacks = []
  
  		callback = obj.AddObserver(eventName, callbackFunction)
  		self._callbacks.append((obj, callback))
  
  	def cleanUpCallbacks(self):
  		"""
  		Cleans up the vtkCallBacks
  		"""
  		if not hasattr(self, "_callbacks"):
  			return
  
  		for obj, callback in self._callbacks:
  			obj.RemoveObserver(callback)
  		self._callbacks = []
  
subject: remove whitespace