how to convert the parameters' unit in SBML using libsbml-python api

[cruise h]

Dear fellow experts:

Me again :(

I  want to do this because  I want to want  to merge SBML files.

I have been working with the problem for days.  i have made a homemade script for the jobs. It seems works for a moment. But it failed very soon. 

Then i checked out the parameter in some SBml files . It contains some units i even don't understand. And i know the units defination maybe usefull, but i don't know how to use it.

Can you give me some advice/tips/methods?

And tell me whether the convert  is just about converting the value in a single parameter?

Thank you very much!