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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 source_add(source, source_type='imgapi'):
    '''
    Add a new source

    source : string
        source url to add
    source_trype : string (imgapi)
        source type, either imgapi or docker

    .. versionadded:: 2019.2.0

    CLI Example:

    .. code-block:: bash

        salt '*' imgadm.source_add https://updates.joyent.com
        salt '*' imgadm.source_add https://docker.io docker
    '''
    ret = {}

    # NOTE: there are some undocumented deprecated source types
    #       so we just warn instead of error on those
    if source_type not in ['imgapi', 'docker']:
        log.warning('Possible unsupported imgage source type specified!')

    cmd = 'imgadm sources -a {0} -t {1}'.format(source, source_type)
    res = __salt__['cmd.run_all'](cmd)
    retcode = res['retcode']
    if retcode != 0:
        ret['Error'] = _exit_status(retcode, res['stderr'])
        return ret

    return sources(False)