docs: def gp_panel(version, skip):
    """example for a panel plot using QM12 data (see gp_xfac)
  
    .. image:: pics/panelQM12.png
       :width: 700 px
  
    :param version: plot version / input subdir name
    :type version: str
    """
    scale = { # QM14 (19 GeV skip later, factor here only informational)
      '19': 1.0340571932983775, '200': 1.0, '39': 0.7776679085382481,
      '27': 0.6412140408244136, '62': 0.9174700031778402
    } if version == 'QM14' else {
        '19': 1.3410566491548412, '200': 1.1051002240771077,
        '39': 1.2719203877292842, '27': 1.350873678084769,
        '62': 1.2664666321635087
    }
    inDir, outDir = getWorkDirs()
    inDir = os.path.join(inDir, version)
    data = {}
    vacRhoTitle = '{/Symbol \162}/{/Symbol \167} VacSF+FB'
    for infile in os.listdir(inDir):
      if infile == "cocktail_contribs": continue
      if infile == 'mediumDmOnly200.dat': continue
      energy = re.compile('\d+').search(infile).group()
      if skip is not None and energy == skip: continue
      data_type = re.sub('%s\.dat' % energy, '', infile)
      file_url = os.path.join(inDir, infile)
      data_import = np.loadtxt(open(file_url, 'rb'))
      if data_type != 'data' and (
          (version == 'QM14' and energy != '19') or version == 'LatestPatrickJieYi'
      ):
         data_import[:,(1,3,4)] /= scale[energy]
      if data_type == 'cocktail': data_import[:,2:] = 0.
      elif fnmatch(data_type, '*medium*') or data_type == 'vacRho':
         data_import = data_import[data_import[:,0] < 0.9] \
                 if energy == '200' and data_type == '+medium' \
                 else data_import
         data_import[:,(2,3)] = 0.
      key = getEnergy4Key(energy)
      if key not in data: data[key] = {}
      data_type_mod = data_type
      if data_type_mod == 'cocktail': data_type_mod = 'Cocktail'
      elif data_type_mod == 'mediumMedOnly': data_type_mod = 'HMBT'
      elif data_type_mod == 'mediumQgpOnly': data_type_mod = 'QGP'
      elif data_type_mod == '+medium': data_type_mod = 'Cock. + HMBT + QGP'
      elif data_type_mod == 'vacRho': data_type_mod = vacRhoTitle
      data[key][data_type_mod] = data_import
    plot_order = ['Cocktail', vacRhoTitle, 'QGP', 'HMBT', 'Cock. + HMBT + QGP', 'data']
    plot_opts = {
      vacRhoTitle: 'with lines lt 2 lw 5 lc %s' % default_colors[6],
      'QGP': 'with lines lt 2 lw 5 lc %s' % default_colors[1],
      'HMBT': 'with lines lt 2 lw 5 lc %s' % default_colors[2],
      'Cock. + HMBT + QGP': 'with filledcurves lt 1 lw 5 pt 0 lc %s' % default_colors[16],
      'Cocktail': 'with lines lc %s lw 5 lt 1' % default_colors[8],
      'data': 'lt 1 lw 4 ps 1.5 lc %s pt 18' % default_colors[0]
    }
    panel2D_versions = (version == 'LatestPatrickJieYi' or version == 'QM14')
    make_panel(
      dpt_dict = OrderedDict(
        (' '.join([k, 'GeV %s' % (
            '{/=18 PRL 113 022301}'
            if k == '200' and (
                version == 'QM12Latest200' or version == 'QM14' or
                version == 'LatestPatrickJieYi'
            ) else '{/=18 STAR Preliminary}'
        )]), [
          [ data[k][dt] for dt in plot_order if dt in data[k] ],
          [ plot_opts[dt] for dt in plot_order if dt in data[k] ],
          [ dt for dt in plot_order if dt in data[k] ]
        ]) for k in sorted(data, key=float)
      ),
      name = os.path.join(
        outDir, 'panel%s%s' % (version, 'No'+skip if skip is not None else '')
      ),
      ylabel = '1/N@_{mb}^{evt} dN@_{ee}^{acc.}/dM_{ee} [ (GeV/c^2)^{-1} ]',
      xlabel = 'invariant dielectron mass, M_{ee} (GeV/c^{2})',
      ylog = True, xr = [0.05, 1.1], yr = [1e-4, 0.5],
      #lmargin = 0.12 if panel2D_versions else 0.1,
      #bmargin = 0.11 if panel2D_versions else 0.15,
      arrow_length = 0.4, arrow_bar = 0.002,
      gpcalls = [
          'mxtics 2',
          'object 50 rectangle back fc rgb "#C6E2FF" from 0.4,1e-4 to 0.75,2e-2'
      ],
      layout = '3x2' if panel2D_versions else ('%dx1' % len(data)),
      key = ['width -2', 'at graph 0.95,0.85'],
      key_subplot_id = 5 if version != 'QM12' else 0,
      size = '8in,8in' if version != 'QM12' else '5in,8.5in'
    )
    return 'done'