def METHOD_NAME(self):
    headers = {
        "accept-encoding": "gzip,deflate",
        "host": "my_host",
        "1st-header": "2",
        "x-osc-date": "20150304T173452Z",
        "user-agent": "my-ua",
    }
    self.assertEqual(
        self.signer._get_canonical_headers(headers),
        "1st-header:2\n"
        "accept-encoding:gzip,deflate\n"
        "host:my_host\n"
        "user-agent:my-ua\n"
        "x-osc-date:20150304T173452Z\n",
    )