您好！我在进行python版mcscan得运行，但是运行到python -m jcvi.graphics.karyotype seqids layout　时，提示错误。

Traceback (most recent call last):
  File "/usr/lib/python2.7/runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/usr/local/lib/python2.7/dist-packages/jcvi/graphics/karyotype.py", line 330, in <module>
    main()
  File "/usr/local/lib/python2.7/dist-packages/jcvi/graphics/karyotype.py", line 318, in main
    Karyotype(fig, root, seqidsfile, layoutfile)
  File "/usr/local/lib/python2.7/dist-packages/jcvi/graphics/karyotype.py", line 294, in __init__
    tr = Track(root, lo, gap=gap, height=height, lw=lw, draw=False)
  File "/usr/local/lib/python2.7/dist-packages/jcvi/graphics/karyotype.py", line 139, in __init__
    ratio = span / total
ZeroDivisionError: float division by zero

我得几个文件是

layout

# y, xstart, xend, rotation, color, label, va,  bed
 .6,     .1,    .8,       0,      , ZM, top, ZM.bed
 .4,     .1,    .8,       0,      , SB, top, SB.bed
# edges
e, 0, 1, ZM.SB.anchors.simple

bed文件：

seqid

chr1,chr2,chr3,chr4,chr5,chr6,chr7,chr8,chr9,chr10
chr1,chr2,chr3,chr4,chr5,chr6,chr7,chr8,chr9,chr10

不知道如何处理这个问题，请您指教。谢谢！