code: public String addClassification(String classificationType) {
          Metadata metadata = new Metadata().add(Metadata.CLASSIFICATION_KEY, classificationType);
          Metadata classification = this.createMetadata(Metadata.CLASSIFICATION_TEMPLATE_KEY,
                  "enterprise", metadata);
  
          return classification.getString(Metadata.CLASSIFICATION_KEY);
      }
docs: Adds a metadata classification to the specified file.
  
  @param classificationType the metadata classification type.
  @return the metadata classification type added to the file.