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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 get_db_prep_value(self, value, connection=None, prepared=False):
 """Returns field's value prepared for interacting with the database backend. Used by the default implementations of ``get_db_prep_save``and `get_db_prep_lookup``` """

        if not value:
            return
        if prepared:
            return value
        else:
            assert(isinstance(value, list) or isinstance(value, tuple))
            return self.separator.join([unicode(s) for s in value])