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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 _attribute_iterator(self, mapped_class, key):
 """ Returns an iterator over the attributes in this mapping for the given mapped class and attribute key. If this is a pruning mapping, attributes that are ignored because of a custom configuration or because of the default ignore rules are skipped. """

        for attr in \
          itervalues_(self.__get_attribute_map(mapped_class, key, 0)):
            if self.is_pruning:
                do_ignore = attr.should_ignore(key)
            else:
                do_ignore = False
            if not do_ignore:
                yield attr