def check_chr(file, lines=100):
    """Checks if a file has lines starting with 'chr'."""
    chrom = False
    count = 0
    with open(file, 'r') as f:
        for line in f:
            if not line.startswith('#'):
                if line.startswith('chr'):
                    chrom = True
                    break
                count += 1
                if count == lines:
                    break
    return chrom
