@atlaskit/adf-schema/dist/esm/schema/marks/unsupported-mark.js

Shared package that contains the ADF-schema (json) and ProseMirror node/mark specs

export var unsupportedMark = {
  toDOM: function toDOM() {
    return ['span'];
  },
  excludes: '',
  attrs: {
    originalValue: {}
  }
};