code: def build_mappings(self):
          
          self.mappings = {}
          for record_type in ('sa', 'sb', 'F8872'):
              path = os.path.join(
                  os.path.dirname(
                      os.path.dirname(
                          os.path.dirname(__file__))),
                  'mappings',
                  '{}.csv'.format(record_type))
              mapping = {}
              with open(path, 'r') as csvfile:
                  reader = csv.DictReader(csvfile)
                  for row in reader:
                      mapping[row['position']] = (
                          row['model_name'],
                          row['field_type'])
  
              self.mappings[record_type] = mapping
docs: Uses CSV files of field names and positions for
          different filing types to load mappings into memory,
          for use in parsing different types of rows.