code: public java.lang.String getRetOrDefault(
        java.lang.String key,
        java.lang.String defaultValue) {
      if (key == null) { throw new java.lang.NullPointerException(); }
      java.util.Map<java.lang.String, java.lang.String> map =
          internalGetRet().getMap();
      return map.containsKey(key) ? map.get(key) : defaultValue;
    }
docs: <pre>
  A mapping from the output arg names from `signature` to the
  outputs from `node_def` that should be returned by the function.
  </pre>
  
  <code>map&lt;string, string&gt; ret = 4;</code>