code: public boolean isNull(String name) {
  		Object value = this.nameValuePairs.get(name);
  		return value == null || value == NULL;
  	}
docs: Returns true if this object has no mapping for {@code name} or if it has a mapping
  whose value is {@link #NULL}.
  @param name the name of the property
  @return true if this object has no mapping for {@code name}