(Optional) A plain object with properties:
     customWarning               [type: String, optional: true]      - Custom text to explain why there is no data.
     customImageUrl              [type: String, optional: true]      - Custom image URL to be used.
     isSimplificationWarning     [type: Boolean, optional: true]     - Indicates there is no data because of a problem with simplifying it.
     isTransparent               [type: Boolean, optional: true]     - Indicates that the background should be semi-transparent.