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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 _parse_argument(self):
 """Parse an argument at the head of the wikicode string."""

        reset = self._head
        try:
            argument = self._parse(contexts.ARGUMENT_NAME)
        except BadRoute:
            self._head = reset
            raise
        self._emit_first(tokens.ArgumentOpen())
        self._emit_all(argument)
        self._emit(tokens.ArgumentClose())