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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 findall(self, title=None):
 """Return a list of worksheets with the given title. Args: title(str):
 title/name of the worksheets to return, or ``None`` for all Returns: list: list of contained worksheet instances (possibly empty) """

        if title is None:
            return list(self._sheets)
        if title not in self._titles:
            return []
        return list(self._titles[title])