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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 derive_field_name(self, field_name):
 """Derives a new event from this one setting the ``field_name`` attribute. Args: field_name (Union[amazon.ion.symbols.SymbolToken, unicode]):
 The field name to set. Returns: IonEvent: The newly generated event. """

        cls = type(self)
        # We use ordinals to avoid thunk materialization.
        return cls(
            self[0],
            self[1],
            self[2],
            field_name,
            self[4],
            self[5]
        )