Please help fix my mcp client error!

I have a simple mcp server setup with streamable http.
mcp server:

mcp = FastMCP(
    name="example server",
    host="127.0.0.1", 
    port=8000
)

if __name__ == "__main__":
    mcp.run(transport="streamable-http")

Also I have created a client to connect to the server.
client:

SERVER_URL = "http://127.0.0.1:8050"

async def connect_to_server(server_url: str):
    async with streamablehttp_client(url=f"{server_url}") as streams:
        async with ClientSession(*streams) as session:
            await session.initialize()

            tools = await session.list_tools()

Then I get the following error:
AttributeError("'function' object has no attribute 'total_seconds'") [single exception in ExceptionGroup]

Additional information: My pytest is setup to run the server as a sub process, then call the client like below, but I'm not convinced this is relevant.

@pytest.fixture(scope="module")
def start_mcp_server():
    print("Starting mcp server as a separate process ...")
    proc = subprocess.Popen(
        ["python", "apps/server/runtime/server.py"],
        stdout=subprocess.PIPE,
        stderr=subprocess.PIPE,
        preexec_fn=os.setsid,
        cwd=BASE_DIR,
        env=env,
    )
    try:
        wait_for_server(f"{SERVER_URL}", timeout=5)
        yield proc
    finally:
        try:
            os.killpg(os.getpgid(proc.pid), signal.SIGTERM)
        except ProcessLookupError:
            pass

@pytest.mark.asyncio
async def test_mcp_server_profile_and_tools(start_mcp_server):
    tools, profile = await connect_to_server(SERVER_URL)