code: public java.lang.String getCallerSuppliedUserAgent() {
      java.lang.Object ref = callerSuppliedUserAgent_;
      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();
        callerSuppliedUserAgent_ = s;
        return s;
      }
    }
docs: <pre>
  The user agent of the caller.
  This information is not authenticated and should be treated accordingly.
  For example:
  +   `google-api-python-client/1.4.0`:
  The request was made by the Google API client for Python.
  +   `Cloud SDK Command Line Tool apitools-client/1.0 gcloud/0.9.62`:
  The request was made by the Google Cloud SDK CLI (gcloud).
  +   `AppEngine-Google; (+http://code.google.com/appengine; appid: s~my-project`:
  The request was made from the `my-project` App Engine app.
  </pre>
  
  <code>string caller_supplied_user_agent = 2;</code>