code: public void appendToString(StringBuilder buffer, String toString) {
          if (toString != null) {
              int pos1 = toString.indexOf(contentStart) + contentStart.length();
              int pos2 = toString.lastIndexOf(contentEnd);
              if (pos1 != pos2 && pos1 >= 0 && pos2 >= 0) {
                  String data = toString.substring(pos1, pos2);
                  if (fieldSeparatorAtStart) {
                      removeLastFieldSeparator(buffer);
                  }
                  buffer.append(data);
                  appendFieldSeparator(buffer);
              }
          }
      }
docs: <p>Append to the <code>toString</code> another toString.</p>
  <p>NOTE: It assumes that the toString has been created from the same ToStringStyle. </p>
  <p/>
  <p>A <code>null</code> <code>toString</code> is ignored.</p>
  
  @param buffer   the <code>StringBuilder</code> to populate
  @param toString the additional <code>toString</code>
  @since 2.0