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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 _lookup_symbols(self, symbols_filename):
 """Look up symbols for actions and action mentions"""

        symbol_lookup = GenewaysSymbols(symbols_filename)
        for action in self.actions:
            action.up_symbol = symbol_lookup.id_to_symbol(action.up)
            action.dn_symbol = symbol_lookup.id_to_symbol(action.dn)