unclosed session when not using a context manager

Question

I built this api wrapper based on https://github.com/mlowijs/tesla_api as suggested by a member of this community as an example/boiler plate on Python Async API Wrapper, how to structure it.

import asyncio
import aiohttp

class AsyncWrapper:
    def __init__(self, api_key, useragent="API-Wrapper/0.2"):
        self.url = f"https://example.api/v1"
        self._api_key = api_key
        self._useragent = useragent
        self._headers = {"X-API-Key": self._api_key, "accept": "application/json", "User-Agent": self._useragent}
        self._session = aiohttp.ClientSession()

    async def __aenter__(self):
        return self

    async def __aexit__(self, exc_type, exc_val, exc_tb):
        await self.close()

    async def close(self):
        await self._session.close()

    async def get_endpoint1(self, arg1, arg2):
        endpoint = "/pair"

        async with self._session.get(self.url + endpoint, params={"arg1": arg1, "arg2": arg2}, headers=self._headers) as response:
            return await response.json()
    
    async def get_endpoint2(self, arg1, arg2, optionalarg1=None, optionalarg2=None):
        endpoint = "/token"

        async with self._session.get(self.url + endpoint, params={"arg1": arg1, "arg2": arg2, "optionalarg1": optionalarg1, "optionalarg2": optionalarg2}, headers=self._headers) as response:
            return await response.json()

The class is done using asynchronous context managers (__aenter__ __aexit__) to create and kill the session as shown here. However, a close() method is left there so it can be called to close the session in case the class wasn't instantiated using a context manager:

class AsyncWrapper:
    def __init__(self, api_key, useragent="API-Wrapper/0.2"):
        self.url = f"https://example.api/v1"
        self._api_key = api_key
        self._useragent = useragent
        self._headers = {"X-API-Key": self._api_key, "accept": "application/json", "User-Agent": self._useragent}
        self._session = aiohttp.ClientSession()

    async def __aenter__(self):
        return self

    async def __aexit__(self, exc_type, exc_val, exc_tb):
        await self.close()

    async def close(self):
        await self._session.close()

When running this code initiating the object, and then closing the session explictly by using the close() method that I left in the class:

import asyncio
import AsyncWrapper

api_key = "my_key"

async def main():
    client = AsyncWrapper(api_key)

    response1 = await client.get_endpoint1("argument1", "argument2")
    print(response1)

    await client.close()

asyncio.run(main())

I get this output claiming unclosed client session. However, the session was explictly closed at the end. After this warning, the output proceeds as normal.

Unclosed client session
client_session: <aiohttp.client.ClientSession object at 0x0000028D1F0E0390>

However, if I run the same code using a context manager. There's no "unclosed client session" warning:

import asyncio
import AsyncWrapper

api_key = "my_key"

async def main():
    async with AsyncWrapper(api_key) as client:
        response1 = await client.get_endpoint1("argument1", "argument2")
        print(response1)

asyncio.run(main())