'Determines whether the file is a velveth produced RoadMap::
142858  21      1
ROADMAP 1
ROADMAP 2'

def sniff(self, filename):

    try:
        fh = open(filename)
        while True:
            line = fh.readline()
            if (not line):
                break
            line = line.strip()
            if line:
                if (not re.match('\\d+\\t\\d+\\t\\d+$', line)):
                    break
                line = fh.readline().strip()
                if (not re.match('ROADMAP    \\d+$', line)):
                    break
                return True
            else:
                break
        fh.close()
    except:
        pass
    return False
