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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 _is_null_value(self, value):
 """ Check if a given value is ``null``. Criteria for this is based on values that shouldn't be included in the Solr ``add`` request at all. """

        if value is None:
            return True

        if IS_PY3:
            # Python 3.X
            if isinstance(value, str) and len(value) == 0:
                return True
        else:
            # Python 2.X
            if isinstance(value, basestring) and len(value) == 0:  # NOQA: F821
                return True

        # TODO: This should probably be removed when solved in core Solr level?
        return False