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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 create(self, name, index=None):
 """ Creates a new sheet with the given name. If an optional index argument is not provided then the created sheet is appended at the end. Returns the new sheet. """

        if index is None:
            index = len(self)
        self._create(name, index)
        return self[name]