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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 get_pid(name, path=None):
    '''
    Returns a container pid.
    Throw an exception if the container isn't running.

    CLI Example:

    .. code-block:: bash

        salt '*' lxc.get_pid name
    '''
    if name not in list_(limit='running', path=path):
        raise CommandExecutionError('Container {0} is not running, can\'t determine PID'.format(name))
    info = __salt__['cmd.run']('lxc-info -n {0}'.format(name)).split("\n")
    pid = [line.split(':')[1].strip() for line in info if re.match(r'\s*PID', line)][0]
    return pid