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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 fname(self, version=None, tags=None, ext=None):
 """Returns the filename appropriate for an instance of this dataset. Parameters version: str, optional The version of the instance of this dataset. tags : list of str, optional The tags associated with the instance of this dataset. ext : str, optional The file extension to use. If not given, the default extension is used. Returns ------- str The appropariate filename. """

        if ext is None:
            ext = self.default_ext
        return '{}{}{}.{}'.format(
            self.fname_base,
            self._tags_to_str(tags=tags),
            self._version_to_str(version=version),
            ext,
        )