code: public Integer getFunctionReturnType(Method m) {
      Class<?> type = m.getReturnType();
  
      if (type == Void.class || type == void.class) {
        return RETURN_VOID;
      }
  
      if (type == Boolean.class || type == boolean.class) {
        return RETURN_BOOLEAN;
      }
  
      if (type == Integer.class || type == int.class || type == Long.class || type == long.class) {
        return RETURN_INTEGER;
      }
  
      if (type == Float.class || type == float.class || type == Double.class || type == double.class) {
        return RETURN_FLOAT;
      }
  
      return RETURN_STRING;
    }
docs: Get idoc function return type.
  
  @param m
  @return