code: function toPropertyNamesArray(propertyNamesString, separator) {
    return propertyNamesString.split(separator || PROPERTY_NAME_SEPARATOR).map(s => trim(s)).filter(s => !!s);
  }
docs: Converts the given property names string into an array of property names
  @param {string} propertyNamesString - a string of property name(s) separated by the given separator
  @param {string|undefined} [separator] - the separator to use to split the property names (defaults to PROPERTY_NAME_SEPARATOR if omitted)
  @returns {Array.<string>} an array of property names (if any)