code: @Pure
  	protected static <VALUET> VALUET unmaskNull(VALUET value) {
  		return (value == NULL_VALUE) ? null : value;
  	}
docs: Unmask the null values given by the used of this map.
  
  <p>This method replaces the internal representation
  {@link #NULL_VALUE} of null values by its user representation
  <code>null</code>.
  
  @param <VALUET> is the type of the value.
  @param value is the value given by the user of this map.
  @return the internal representation of the value.
  @see #maskNull(Object)