function getProxyUrl(serverUrl) {
	    const proxyUrl = pm.getProxyUrl(new URL(serverUrl));
	    return proxyUrl ? proxyUrl.href : '';
	}
Creates a {@link WritableStreamDefaultWriter | writer} and locks the stream to the new writer. While the stream
is locked, no other writer can be acquired until this one is released.

This functionality is especially useful for creating abstractions that desire the ability to write to a stream
without interruption or interleaving. By getting a writer for the stream, you can ensure nobody else can write at
the same time, which would cause the resulting written data to be unpredictable and probably useless.