In python is there a way to check if a function is a "generator function" before calling it?

Lets say I have two functions:

def foo():
  return 'foo'

def bar():
  yield 'bar'

The first one is a normal function, and the second is a generator function. Now I want to write something like this:

def run(func):
  if is_generator_function(func):
     gen = func()
     gen.next()
     #... run the generator ...
  else:
     func()

What will a straightforward implementation of is_generator_function() look like? Using the types package I can test if gen is a generator, but I wish to do so before invoking func().

Now consider the following case:

def goo():
  if False:
     yield
  else:
     return

An invocation of goo() will return a generator. I presume that the python parser knows that the goo() function has a yield statement, and I wonder if it possible to get that information easily.

Thanks!