@java.lang.Override
  public /* nullable */ java.lang.String getUserEnvVarsOrDefault(
      java.lang.String key,
      /* nullable */
      java.lang.String defaultValue) {
    if (key == null) {
      throw new NullPointerException("map key");
    }
    java.util.Map<java.lang.String, java.lang.String> map = internalGetUserEnvVars().getMap();
    return map.containsKey(key) ? map.get(key) : defaultValue;
  }
<pre>
Optional. User-defined environment variables associated with this workflow
revision. This map has a maximum length of 20. Each string can take up to
4KiB. Keys cannot be empty strings and cannot start with "GOOGLE" or
"WORKFLOWS".
</pre>

<code>map&lt;string, string&gt; user_env_vars = 14 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-workflows/proto-google-cloud-workflows-v1/src/main/java/com/google/cloud/workflows/v1/Workflow.java