code: public boolean resetToDefault(String propertyName)
      {
          gatekeeper.signIn();
          try
          {
              /*
               * If this property was added with no default value, all we can do
               * is remove the property entirely.
               */
              String defaultValue = getDefaultValue(propertyName);
              if (defaultValue == null)
              {
                  return properties.remove(propertyName) != null;
              }
  
              /*
               * Every property with a default value is guaranteed to have a
               * stack. Since we just confirmed the existence of a default value,
               * we know the stack is available.
               */
              return properties.get(propertyName).push(defaultValue);
          }
          finally
          {
              gatekeeper.signOut();
          }
      }
docs: Reset the value associated with specified property to its default value.
  
  @param propertyName
  the property whose associated value should be reset
  @return <code>true</code> if the value of the given property changed as a
  result of this call; <code>false</code> otherwise