How can I know an instance is necessary to work module?

[forester3]

Hi,
I have a question.
How can I know an instance is necessary to work module?

For example,
pyb.Pin.board.LED.on()
This will work without an instance.

However,
pyb.RTC.datetime()
This dose not work.
rtc = pyb.RTC()
rtc.datetime()
This works.

I can imagine that this difference depends on how to make a module.
How people who do not see the source of the module can find this diffrence?

[deshipu]

We read the documentation.

[forester3]

Thank you, for your ans.

I have known pyb.RTC() sample code in documents.
However, there are many module functions without sample code in documents.

I felt uneasy and asked a question.

[kevinkk525]

If you ask about a module without documentation, you might get an answer. But theser are documented.