docs: public com.squareup.okhttp.Call deleteCharactersCharacterIdMailMailIdAsync(Integer characterId, Integer mailId,
              String datasource, String token, final ApiCallback<Void> callback) throws ApiException {
  
          com.squareup.okhttp.Call call = deleteCharactersCharacterIdMailMailIdValidateBeforeCall(characterId, mailId,
                  datasource, token, callback);
          apiClient.executeAsync(call, callback);
          return call;
      }