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

def compute_samples(channels, nsamples=None):
    '''
    create a generator which computes the samples.
    essentially it creates a sequence of the sum of each function in the channel
    at each sample in the file for each channel.
    '''
    return islice(izip(*(imap(sum, izip(*channel)) for channel in channels)), nsamples)