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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def trees_by_path(self, path):
 """ Search trees by `path`. Args: path (str):
 :attr:`.Tree.path` property of :class:`.Tree`. Returns: set: Set of matching :class:`Tree` instances. """

        return set(
            self.path_db.get(path, OOSet()).keys()
        )