code: public Object getMappedValue(Property property, Object key) {
          return getMappedValue(object, property, key);
      }
docs: Returns the value of the specified mapped property from the wrapped object.
  
  @param property the mapped property whose value is to be extracted, cannot be {@code null}
  @param key      the key of the property value to be extracted, can be {@code null}
  @return the mapped property value
  @throws ReflectionException      if a reflection error occurs
  @throws IllegalArgumentException if the property parameter is {@code null}
  @throws IllegalArgumentException if the mapped object in the wrapped object is not a {@link Map} type
  @throws NullPointerException     if the mapped object in the wrapped object is {@code null}