code: public boolean containsExternalValues(
        java.lang.String key) {
      if (key == null) { throw new java.lang.NullPointerException(); }
      return internalGetExternalValues().getMap().containsKey(key);
    }
docs: <pre>
  Value names referenced by but external to this context.
  </pre>
  
  <code>map&lt;string, string&gt; external_values = 2;</code>