Longest subsequence of two unique elements

def find_long_sseq(seq):
    """Find the longest subsequence of seq which contains
    no more than two distinct elements"""
    if len(seq) < 3:
        return seq
    max_sub = seq[:2]
    max_len = 2
    curr_sub = seq[:2]
    if seq[0]==seq[1]:
        change_index = 0
    else:
        change_index = 1
    for index, item in enumerate(seq):
        if index < 2:
            continue
        if item in curr_sub:
            curr_sub.append(item)
            if item != seq[change_index]:
                change_index = index
        else:
            curr_sub = seq[change_index:index+1]
            change_index = index
        n = len(curr_sub)
        if n > max_len:
            max_sub = curr_sub
            max_len = n
    return max_sub