<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def show(*args, **kw):
 """Print value of IRAF or OS environment variables."""


    if len(kw):
        raise TypeError('unexpected keyword argument: %r' % list(kw))

    if args:
        for arg in args:
            print(envget(arg))
    else:
        # print them all
        listVars(prefix="    ", equals="=")