Using Python defined functions in packages ..

Using Vim.. Python programing seems easier because YCM helps presenting all the arguments required in its order.. But there's one more problem that's usually hard to solve, yes it's aka the **kwargs.. in functions.. and yes, Vim has no prompt about what it is..

So after googling.. 

A module called inspect is useful when previewing the functions.. Usage:

from django.db import models # the function used is in this module.
import inspect
inspect.getargspec(models.IntegerField)

# the function's argument list does not present in YCM ..
# but the inspcet module works fine.. and seems to be always working

# also can be :
inspect.getfullargspec(models.IntegerField)

Have fun.