This is not supported yet. The abstractions we use for parameters in C++ rely on templates and I believe we cannot easily transfer them to python. We have been looking into workarounds but the priority is not so high compared to other items so it might take a while,
In the meantime, your best bet is to add custom commands, and then set the parameters using those commands from the console in the inventor.
see for example
http://jevois.org/doc/PythonTutorial3_8py_source.html
you implement parseSerial() to decode received commands that use command names that are not already used by the JeVois engine. Then also implement supportedCommands() to provide some help message.
for example, you could define a new command which you would want to type in the console of the inventor:
setMinHue value
in parseSerial() you get the whole line of text that was entered in the command-line by the user. So just break it into tokens, then if the first token is "setMinHue" convert the second token to a number an update the internal parameter of your module that handles the min hue with that number.
more info about parseSerial() is here:
http://jevois.org/doc/ProgrammerPython.html