code: def precall(data):
      
      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)
docs: Perform initial pre-calling steps -- coverage calcuation by sample.
  
      Use mosdepth to call average region coverage in regions, and convert
      into seq2c format.