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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def docker_pull(image):
    '''Pulls an image'''
    args = ['docker', 'pull', image]

    # If this fails, the default docker stdout/stderr looks good to the user.
    ret = call(args)
    if ret != 0:
        raise DockerError('Failed to pull image "{}"'.format(image))