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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 projection(self, projection):
 """Set the fields returned the query. :type projection: str or sequence of strings :param projection: Each value is a string giving the name of a property to be included in the projection query. """

        if isinstance(projection, str):
            projection = [projection]
        self._projection[:] = projection