<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def _zip_flatten(x, ys):
    '''
    intersperse x into ys, with an extra element at the beginning.
    '''
    return itertools.chain.from_iterable(
            zip(itertools.repeat(x), ys))