def startswith_(a, fragment, msg=None):
    assert a.startswith(fragment), msg or "%r does not start with %r" % (
        a, fragment)
Assert a.startswith(fragment), with repr messaging on failure.
dataset/ETHPy150Open RoseOu/flasky/venv/lib/python2.7/site-packages/sqlalchemy/testing/assertions.py/startswith_