When I read Pytest’s documentation for pytest_runtest_setup(), it said as below:

pytest_runtest_setup(item)[source]¶ Called to perform the setup phase
for a test item.

The default implementation runs setup() on item and all of its parents
(which haven’t been setup yet). This includes obtaining the values of
fixtures required by the item (which haven’t been obtained yet).

I wonder for the setup() quoted here, is it a real built in function that Pytest framework included, if it is, however I did not find the documentation for this function, I only find some related documenations for setup method like this, can someone give some tips to clarify, thanks!