code: public Map<String, String> getEnvironment() throws AppEngineException {
      Node environmentParentNode = getNode(document, "appengine-web-app", "env-variables");
      if (environmentParentNode != null) {
        return getAttributeMap(environmentParentNode, "env-var", "name", "value");
      }
      return new HashMap<>();
    }
docs: Given the following structure:
  
  <pre>{@code
  <env-variables>
  <env-var name="key" value="val" />
  </env-variables>
  }</pre>
  
  <p>This will construct a map of the form {[key, value], ...}.
  
  @return a map representing the environment variable settings in the appengine-web.xml