docs: public String[] getFamilyNames() {
      HashSet<String> familyNameSet = new HashSet<String>();
  
      if (familyNames == null) {
        for (String columnName : columns(null, this.valueFields)) {
          int pos = columnName.indexOf(":");
          familyNameSet.add(hbaseColumn(pos > 0 ? columnName.substring(0, pos) : columnName));
        }
      } else {
        for (String familyName : familyNames) {
          familyNameSet.add(familyName);
        }
      }
      return familyNameSet.toArray(new String[0]);
    }