Combined Python context manager, iterator, and iterable; with a generator-like send() method

cm.py

EVENS = object()
STOP = object()


class CM():
    def __init__(self, n=10):
        print('__init__() called')
        self.n = n
        self._it = iter(range(n))
        self._evens = False
        self._stop = False

    @staticmethod
    def is_odd(n):
        return n % 2

    # Context Manager protocol
    def __enter__(self):
        print('__enter__() called')
        return self

    # exc_* are None on the happy path, otherwise Return True to suppress 
    def __exit__(self, exc_type, exc_value, exc_traceback):
        print('__exit__() called')
 
    # Iterable protocol
    def __iter__(self):
        print('__iter__() called')
        return self

    # Iterator protocol
    def __next__(self):
        if self._stop:
            raise StopIteration
        v = next(self._it)
        if self._evens and self.is_odd(v):
            v = next(self._it)
        return v

    def send(self, value):
        if value is EVENS:
            self._evens = value
        if value is STOP:
            self._stop = value


if __name__ == '__main__':
    with CM() as cm:
        for i in cm:
            print(i)
            if i == 1:
                cm.send(EVENS)
            if i >= 6:
                cm.send(STOP)