def get_seqs_dic_repeat_region_ratios(seqs_dic):
    """
    Given a dictionary of sequences, calculate the repeat region content /
    ratio for each site. Return dictionary of repeat region ratios.

    >>> seqs_dic = {'s1' : "ACGUacgu", 's2' : "acnacnACNacn", 's3' : "A", 's4' : "u"}
    >>> get_seqs_dic_repeat_region_ratios(seqs_dic)
    {'s1': 0.5, 's2': 0.75, 's3': 0.0, 's4': 1.0}

    """
    assert seqs_dic, "seqs_dic empty"

    ratios_dic = {}
    for seq_id in seqs_dic:
        seq = seqs_dic[seq_id]
        seq_l = len(seq)
        c_r = 0
        for nt in seq:
            if nt.islower():
                c_r += 1
        r_ratio = c_r / seq_l
        ratios_dic[seq_id] = r_ratio
    assert ratios_dic, "ratios_dic empty"
    return ratios_dic