def split_nth(seq, separator, n):
    """
    Split sequence at the n-th occurence of separator

    Args:
        seq(str) : sequence to split
        separator(str): separator to split on
        n(int) : split at the n-th occurence
    """
    pos = 0
    for i in range(n):
        pos = seq.index(separator, pos + 1)

    return seq[:pos], seq[pos + 1:]