code: private InputSource getCMLType(String type) {
          try {
              InputStream ins = this.getClass().getClassLoader()
                      .getResourceAsStream("org/openscience/cdk/io/cml/data/" + type);
              return new InputSource(new BufferedReader(new InputStreamReader(ins)));
          } catch (Exception e) {
              logger.error("Error while trying to read CML DTD (" + type + "): ", e.getMessage());
              logger.debug(e);
              return null;
          }
      }
docs: Returns an InputSource of the appropriate CML DTD. It accepts
  two CML DTD names: cml1_0.dtd and cml1_0_1.dtd. Returns null
  for any other name.
  
  @param type the name of the CML DTD version
  @return the InputSource to the CML DTD