def asRanges(gffs, feature=None):

    if isinstance(feature, basestring):
        gg = filter(lambda x: x.feature == feature, gffs)
    elif feature:
        gg = filter(lambda x: x.feature in feature, gffs)
    else:
        gg = gffs[:]

    r = [(g.start, g.end) for g in gg]
    return Intervals.combine(r)
return ranges within a set of gffs.
dataset/ETHPy150Open CGATOxford/cgat/CGAT/GTF.py/asRanges