Perform initial pre-calling steps -- coverage calcuation by sample.

    Use mosdepth to call average region coverage in regions, and convert
    into seq2c format.

def precall(data):
    """Perform initial pre-calling steps -- coverage calcuation by sample.

    Use mosdepth to call average region coverage in regions, and convert
    into seq2c format.
    """
    data = utils.to_single_data(data)
    bed_file = tz.get_in(["config", "algorithm", "seq2c_bed_ready"], data)
    if not bed_file:
        raise ValueError("Error: svregions or variant_regions BED file required for Seq2C")
    sample_name = dd.get_sample_name(data)
    work_dir = _sv_workdir(data)
    return _calculate_coverage(data, work_dir, bed_file, sample_name)