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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 has_builder(self):
 """Return whether this Node has a builder or not. In Boolean tests, this turns out to be a *lot* more efficient than simply examining the builder attribute directly ("if directly, it ends up calling __getattr__ for both the __len__ and __nonzero__ attributes on instances of our Builder Proxy class(es), generating a bazillion extra calls and slowing things down immensely. """

        try:
            b = self.builder
        except AttributeError:
            # There was no explicit builder for this Node, so initialize
            # the self.builder attribute to None now.
            b = self.builder = None
        return b is not None