Retrieve a ``RuleDoc`` object from the ``Policy`` with the
        given name.  The ``RuleDoc`` object contains all documentation
        for the named rule.

        :param name: The name of the rule to retrieve the
                     documentation for.

        :returns: A ``RuleDoc`` object containing the documentation
                  for the rule.

def get_doc(self, name):
        """
        Retrieve a ``RuleDoc`` object from the ``Policy`` with the
        given name.  The ``RuleDoc`` object contains all documentation
        for the named rule.

        :param name: The name of the rule to retrieve the
                     documentation for.

        :returns: A ``RuleDoc`` object containing the documentation
                  for the rule.
        """

        # Create one if there isn't one already
        if name not in self._docs:
            self._docs[name] = rules.RuleDoc(name)

        return self._docs[name]