code: 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;
      }
docs: List versions (asynchronously) List all endpoint versions
  
  @param userAgent
  Client identifier, takes precedence over headers (optional)
  @param xUserAgent
  Client identifier, takes precedence over User-Agent (optional)
  @param callback
  The callback to be executed when the API call finishes
  @return The request call
  @throws ApiException
  If fail to process the API call, e.g. serializing the request
  body object