def base_content(seq: str, base: str) -> float:
    """
    Compute the fraction of <base> in the <seq>

    Args
        seq:
            DNA sequence

        base:
            'A' gives the A content; 'GC' gives the GC content
    """
    seq = seq.upper()
    base = base.upper()

    ret = 0
    for b in set(base):
        ret += seq.count(b) / len(seq)
    return ret