code: def _create_polynomial_model(
      name: str,
      symbol: str,
      degree: int,
      ds: DataSet,
      dss: dict):
      
      ds_name = ds.name.split(".")[0].lower()
      file_name = f"{name.lower()}-{symbol.lower()}-polynomialmodelt-{ds_name}"
      newmod = PolynomialModelT.create(ds, symbol, degree)
      newmod.plot(dss, _path(f"data/{file_name}.pdf"), False)
      newmod.write(_path(f"data/{file_name}.json"))
docs: Create a polynomial model to describe the specified property based on the
      specified data set, and save it to a .json file.
  
      :param name: material name.
      :param symbol: property symbol.
      :param degree: polynomial degree.
      :param ds: the source data set.
      :param dss: dictionary of all datasets.