static getId(marker = '', namespace = '', name) {

    return name
      ? marker + (namespace && `${namespace}:`) + name
      : 'tmap:unknown';

  }
Creates an {@link EdgeTypeId} from a set of parts that make up the id.
If it is not possible to create the id from the parts, the default
edge type 'tmap:unknown' is returned.

@param {string} marker
@param {string} namespace
@param {string} name
@return {EdgeTypeId}