code: def _read_index_file(self):
          
          param_file = os.path.join(self.index_dir, self.param_file)
          with open(param_file) as f:
              for line in f.readlines():
                  (name, fasta_file, index_file, line_size, total_size) = line.strip().split("\t")
                  self.size[name] = int(total_size)
                  self.fasta_file[name] = fasta_file
                  self.index_file[name] = index_file
                  self.line_size[name] = int(line_size)
docs: read the param_file, index_dir should already be set