Cell interface is a base for built-in cell templates and your own, it has only one necessary property - type.
Definition
interface Cell {
    type: string;
    groupId?: Id;
    style?: CellStyle;
    className?: string;
}Properties
| Properties | Type | Properties description | 
|---|---|---|
| type | string | Name of cell type, must be unique | 
| groupId | Id | Idof group to which this cell belongs to | 
| style? | CellStyle | Allowed style properties contained in CellStyleinterface | 
| className? | string | Additional CSS classes |