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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_cached_source_variable(self, source_id, variable, default=None):
 """ Get the cached value of a source variable. If the variable is not cached return the default value. """


        source_id = int(source_id)
        try:
            return self._retrieve_cached_source_variable(
                    source_id, variable)
        except UncachedVariable:
            return default