code: public String updateClassification(String classificationType) {
          Metadata metadata = new Metadata("enterprise", Metadata.CLASSIFICATION_TEMPLATE_KEY);
          metadata.add("/Box__Security__Classification__Key", classificationType);
          Metadata classification = this.updateMetadata(metadata);
  
          return classification.getString(Metadata.CLASSIFICATION_KEY);
      }
docs: Updates a metadata classification on the specified file.
  
  @param classificationType the metadata classification type.
  @return the new metadata classification type updated on the file.