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'''
:copyright: Copyright 2006-2009 by Oliver Schoenborn, all rights reserved.
:license: BSD, see LICENSE.txt for details.
'''
class ITopicTreeVisitor:
'''
Topic tree traverser. Provides the traverse() method
which traverses a topic tree and calls self._onTopic() for
each topic in the tree that satisfies self._accept().
Additionally it calls self._startChildren() whenever it
starts traversing the subtopics of a topic, and
self._endChildren() when it is done with the subtopics.
Finally, it calls self._doneTraversal() when traversal
has been completed.
Derive from ITopicTreeVisitor and override one or more of the
four self._*() methods described above. Give an instance to
an instance of pub.TopicTreeTraverser, whose traverse()
method will cause the tree to be printed.
'''
def _accept(self, topicObj):
'''Override this to filter nodes of topic tree. Must return
True (accept node) of False (reject node). Note that rejected
nodes cause traversal to move to next branch (no children
traversed).'''
return True
def _startTraversal(self):
'''Override this to define what to do when traversal() starts.'''
pass
def _onTopic(self, topicObj):
'''Override this to define what to do for each node.'''
pass
def _startChildren(self):
'''Override this to take special action whenever a
new level of the topic hierarchy is started (e.g., indent
some output). '''
pass
def _endChildren(self):
'''Override this to take special action whenever a
level of the topic hierarchy is completed (e.g., dedent
some output). '''
pass
def _doneTraversal(self):
'''Override this to take special action when traversal done.'''
pass
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