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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 login(username, password, development_mode=False):
 """Return the user if successful, None otherwise"""

        retval = None
        try:
            user = User.fetch_by(username=username)
            if user and (development_mode or user.verify_password(password)):
                retval = user
        except OperationalError:
            pass
        return retval