def __init__ ( self, added = None, changed = None, removed = None ):
        """
        Parameters
        ----------
        added : dict
            New keys and values.
        changed : dict
            Updated keys and their previous values.
        removed : dict
            Old keys and values that were just removed.
        """
        # Construct new empty dicts every time instead of using a default value
        # in the method argument, just in case someone gets the bright idea of
        # modifying the dict they get in-place.
        if added is None:
            added = {}
        self.added = added

        if changed is None:
            changed = {}
        self.changed = changed

        if removed is None:
            removed = {}
        self.removed = removed

#-------------------------------------------------------------------------------
#  'TraitDict' class:
#-------------------------------------------------------------------------------
dataset/ETHPy150Open enthought/traits/traits/trait_handlers.py/TraitDictEvent.__init__/original