Some keywords accept configuration parameters as **configuration or **config and then read accepted parameters from the resulting dictionary. For example, OperatingSystem has this kind of code:

def append_to_environment_variable(self, name, *values, **config):
    separator = config.pop('separator', os.pathsep)
    if config:
        raise TypeError(...)
    ...

The reason for this configuration approach is that with Python 2 it wasn't possible to have configuration options after *varargs like:

def append_to_environment_variable(self, name, *values, separator=os.pathsep):
    ...

Python 3 supports the above just fine and Robot has supported these named-only arguments for ages as well. We should update keywords so that they use named-only arguments instead of **config for the following reasons:

• Simpler code.
• Better documentation in Libdoc. Parameters are named explicitly instead of just mentioned in the documentation.
• Much easier to add type hints (Add type hints to the standard libraries #5373).

Based on my search these keywords need to be updated:

• OperatingSystem.append_to_environment_variable
• BuiltIn.should_contain_any
• BuiltIn.should_not_contain_any
• Process.run_process
• Process.start_process

It would be good to get these updated already in RF 7.3 so that people interested in adding type hints (#5373) in RF 7.4 don't need to wait. Three first ought to be easy to fix, but the last two are a little bit more complicated, because they also accept environment variables freely using format env:name=value. They thus need to continue to accept **extra_env or something like that. If that gets too complicated, fixing Process keywords can wait for RF 7.4.