Cast using python type annotations

cast.py

def cast(f):
    returns = f.__annotations__['return']
    if callable(returns):
        casters = returns,
    else:
        casters = reversed(returns)
    def inner(*args, **kwargs):
        r = f(*args, **kwargs)
        for caster in casters:
            r = caster(r)
        return r
    return inner

@cast
def nums() -> dict:
    yield 1, 'one'
    yield 2, 'two'

@cast
def hello() -> (str.upper, ', '.join):
    yield "Hello"
    yield "world"

print(repr(nums()))
print(repr(hello()))
"""
{1: 'one', 2: 'two'}
'HELLO, WORLD'
"""