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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 sources_list(ruby=None, runas=None, gem_bin=None):
    '''
    List the configured gem sources.

    :param gem_bin: string : None
        Full path to ``gem`` binary to use.
    :param ruby: string : None
        If RVM or rbenv are installed, the ruby version and gemset to use.
        Ignored if ``gem_bin`` is specified.
    :param runas: string : None
        The user to run gem as.

    CLI Example:

    .. code-block:: bash

        salt '*' gem.sources_list
    '''
    ret = _gem(['sources'], ruby, gem_bin=gem_bin, runas=runas)
    return [] if ret is False else ret.splitlines()[2:]