example.py

import asyncio
from _pytest.compat import is_generator

async def foo():
    await foo()

async def bar():
    pass

print(is_generator(foo))

from _pytest._code import getrawcode

print(is_generator(foo))
print(is_generator(bar))

@asyncio.coroutine
def baz():
    yield from bar()

def zap():
    yield

print(is_generator(baz))
print(is_generator(zap))

output

$ python example.com
False
32
0
32
32