static getRegisteredSubtypes() {
    const types = {}
    for (const key in control.classRegister) {
      if (control.classRegister.hasOwnProperty(key)) {
        const [type, subtype] = key.split('.')
        if (!subtype) {
          continue
        }
        if (!types[type]) {
          types[type] = []
        }
        types[type].push(subtype)
      }
    }
    return types
  }
Retrieves an object of types mapped to an array of subtypes.
Only returns types that have subtypes
@return {Object} an object containing {type: array of subtypes}.