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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 return_features(self, names='all'):
 """ Returns a list of extracted features from the database Parameters names : list of strings, a list of feature names which are to be retrieved from the database, if equal to 'all', the all features will be returned, default value: 'all' Returns ------- A list of lists, each 'inside list' corresponds to a single data point, each element of the 'inside list' is a feature (can be of any type) """

        if self._prepopulated is False:
            raise errors.EmptyDatabase(self.dbpath)
        else:
            return return_features_base(self.dbpath, self._set_object, names)