def vlink(s_expnum, s_ccd, s_version, s_ext,
          l_expnum, l_ccd, l_version, l_ext, s_prefix=None, l_prefix=None):
    """make a link between two version of a file.

    @param s_expnum:
    @param s_ccd:
    @param s_version:
    @param s_ext:
    @param l_expnum:
    @param l_ccd:
    @param l_version:
    @param l_ext:
    @param s_prefix:
    @param l_prefix:
    @return:
    """
    source_uri = get_uri(s_expnum, ccd=s_ccd, version=s_version, ext=s_ext, prefix=s_prefix)
    link_uri = get_uri(l_expnum, ccd=l_ccd, version=l_version, ext=l_ext, prefix=l_prefix)

    return client.link(source_uri, link_uri)
make a link between two version of a file.

    @param s_expnum:
    @param s_ccd:
    @param s_version:
    @param s_ext:
    @param l_expnum:
    @param l_ccd:
    @param l_version:
    @param l_ext:
    @param s_prefix:
    @param l_prefix:
    @return: