def update_not_existing_kwargs(to_update, update_from):
if to_update is None:<EOL><INDENT>to_update = {}<EOL><DEDENT>to_update.update({k:v for k,v in update_from.items() if k not in to_update})<EOL>return to_update<EOL>
This function updates the keyword aguments from update_from in
to_update, only if the keys are not set in to_update.

This is used for updated kwargs from the default dicts.