code: public org.tensorflow.framework.SignatureDef getSignatureDefOrDefault(
        java.lang.String key,
        org.tensorflow.framework.SignatureDef defaultValue) {
      if (key == null) { throw new java.lang.NullPointerException(); }
      java.util.Map<java.lang.String, org.tensorflow.framework.SignatureDef> map =
          internalGetSignatureDef().getMap();
      return map.containsKey(key) ? map.get(key) : defaultValue;
    }
docs: <pre>
  signature_def: Map from user supplied key for a signature to a single
  SignatureDef.
  </pre>
  
  <code>map&lt;string, .tensorflow.SignatureDef&gt; signature_def = 5;</code>