def get_seq_lengths_from_seqs_dic(seqs_dic):
    """
    Given a dictionary of sequences, return dictionary of sequence lengths.
    Mapping is sequence ID -> sequence length.
    """
    seq_len_dic = {}
    assert seqs_dic, "sequence dictionary seems to be empty"
    for seq_id in seqs_dic:
        seq_l = len(seqs_dic[seq_id])
        seq_len_dic[seq_id] = seq_l
    return seq_len_dic