code: public boolean isPresent(final String propertyName) {
      for (String configurationPropertyName : this) {
        if (configurationPropertyName.equals(propertyName)) {
          return true;
        }
      }
  
      return false;
    }
docs: Determines whether the configuration property identified by name is present in the configuration settings, which
  means the configuration property was declared but not necessarily defined.
  
  @param propertyName a String value indicating the name of the configuration property.
  @return a boolean value indicating if the property identified by name is present (declared) in the configuration
  settings.
  @see #isSet(String)