docs: public com.squareup.okhttp.Call getVersionsAsync(String userAgent, String xUserAgent,
              final ApiCallback<List<String>> callback) throws ApiException {
  
          com.squareup.okhttp.Call call = getVersionsValidateBeforeCall(userAgent, xUserAgent, callback);
          Type localVarReturnType = new TypeToken<List<String>>() {
          }.getType();
          apiClient.executeAsync(call, localVarReturnType, callback);
          return call;
      }