code: public String getOrderFieldName () {
          String name = fields[1].name;
          if (name.contains("_sequence") || compoundKey) return name;
          else return null;
      }
docs: Returns field name that defines order for grouped entities or that defines the compound key field (e.g.,
  transfers#to_stop_id). WARNING: this field must be in the 1st position (base zero) of the fields array; hence,
  this MUST be called on a spec table (i.e., one of the constant tables defined in this class). Otherwise, it could
  return null even if the table has an order field defined.