The caption for the encoding. Will be rendered as the legend group caption.
The encoding channel. Can be either "color" or "size"
An optional data object that is referenced by this encoding.
The slot that this encoding is assigned to.
An optional sub caption for the encoding.
The type of the encoding, either "cat" or "cont".
Categorical encoding. Instance can be created given a slot, palette and some meta information. Instances of CatEncoding can be returned to a host for creating (swatch) legends.