code: public java.lang.String getExplanation() {
      java.lang.Object ref = explanation_;
      if (ref instanceof java.lang.String) {
        return (java.lang.String) ref;
      } else {
        com.google.protobuf.ByteString bs = 
            (com.google.protobuf.ByteString) ref;
        java.lang.String s = bs.toStringUtf8();
        explanation_ = s;
        return s;
      }
    }
docs: <pre>
  Explanation of why it was deprecated and what to use instead.
  </pre>
  
  <code>optional string explanation = 2;</code>