M5stack | Micropython API

[th100]

Hi,
Where can I find the source code of the following:
m5stack, m5stack_ui, uiflow..
If it's not possible then where can I find a documentation for the functions they contain??
For example: https://docs.m5stack.com/en/mpy/display/m5stack_lvgl
In the above link they describe Micropython LVGL, but they don't give any information about the API.. How can I write code if I don't know anything about what I have in hand??
I'd appreciate any help.

Thanks in advance!