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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 list_symbols(self, partial_match=None):
 """ Returns all symbols in the library Parameters partial: None or str if not none, use this string to do a partial match on symbol names Returns ------- list of str """

        symbols = self._symbols.distinct(SYMBOL)
        if partial_match is None:
            return symbols
        return [x for x in symbols if partial_match in x]