def _create_dirs(idir, dirs):
    '''
    Create a set of directories, so we could store the input files.
    For example, seq1 could be stored under:
        /in/seq1/NC_001122.fasta

    TODO: this call could fail, we need to report a reasonable error code

    Note that we create a directory for every file array, even if
    it has zero inputs.
    '''
    # create the <idir> itself
    file_load_utils.ensure_dir(idir)
    # create each subdir
    for d in dirs:
        file_load_utils.ensure_dir(os.path.join(idir, d))