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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 df(self, version=None, tags=None, ext=None, **kwargs):
 """Loads an instance of this dataset into a dataframe. Parameters version: str, optional The version of the instance of this dataset. tags : list of str, optional The tags associated with the desired instance of this dataset. ext : str, optional The file extension to use. If not given, the default extension is used. **kwargs : extra keyword arguments, optional Extra keyword arguments are forwarded to the deserialization method of the SerializationFormat object corresponding to the extension used. Returns ------- pandas.DataFrame A dataframe containing the desired instance of this dataset. """

        ext = self._find_extension(version=version, tags=tags)
        if ext is None:
            attribs = "{}{}".format(
                "version={} and ".format(version) if version else "",
                "tags={}".format(tags) if tags else "",
            )
            raise MissingDatasetError(
                "No dataset with {} in local store!".format(attribs))
        fpath = self.fpath(version=version, tags=tags, ext=ext)
        fmt = SerializationFormat.by_name(ext)
        return fmt.deserialize(fpath, **kwargs)