Date as string in RFC3339 format (YYYY-MM-DD).

JPEG indicates a standard .jpeg image.

PNG indicates a standard .png image.

STRING means the value is UTF-8 encoded text.

UNDEFINED should not be seen, and is used as an error placeholder value.

AttributeAndId is a simple container for holding an attribute's value alongside its ID.

ContentType indicates how to interpret the ‘Value’ field of an Attribute.