One of the following values as well as value_ptr containing an unparsed string with the address of the location of the value.
If no error is detected.
If the properties, key, or value_ptr argument is NULL.
If the specified key has no associated value and a default value is not provided.
If the value associated with the specified key is cannot be parsed as required by the particular accessor function.
If insufficient memory is available to look up the key.