def __init__(self, filename):
        super(BinMap, self).__init__(filename)

        fp = open(filename)
        for header, seq in read_block(fp, "group "):
            lg = header.split()[-1]
            self[lg] = []
            for s in seq:
                if s.strip() == "" or s[0] == ";":
                    continue
                marker, pos = s.split()
                pos = int(float(pos) * 1000)
                self[lg].append((marker, pos))