First check

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Hello!

I've noticed, that aiohttp is simply concatenating server-response (or client-request) header like this, w/o any validation:

    line = status_line + '\r\n' + ''.join(
        [k + ': ' + v + '\r\n' for k, v in headers.items()])

Which may be not okay, if some of the header values were based on user input.

Consider this example:

import aiohttp.web
asyn

Our environment variable documentation should include some justification or context for each case, by doing one of the following for each envvar:

• Make it clear that an environment variable is specific to HTTPX. (Probably only relevant to anything prefixed by HTTPX_)
• Make it clear that an environment variable is used as a convention by

Great stuff! I'd love to use this in magic-wormhole.. I only need the DataChannel, though. Any idea how hard it'd be to define a 'feature' for the codecs, so pip install aiortc[video] gets you the dependencies on the codecs, but pip install aiortc[datachannel] does not?

Example of usage:

users = await User.filter(first_name__ilike="c%r")

I know this can be done with startswith and endswith, but there are cases where using the LIKE operator is better:

users = await User.filter(first_name__ilike="j_r%")

This would be used to match Jeremy, Jorge, Jordan...

Summary

Fixed Bad Request: unsupported parse_mode error due to missing prepare_parse_mode line

P.S. Do I have to cover this case by tests?

UPD. May be a bit related to #387