code: public static Class<?> resolveReturnType(Method method, Class clazz) {
  		Preconditions.checkNotNull(method, "Method must not be null");
  		Type genericType = method.getGenericReturnType();
  		Preconditions.checkNotNull(clazz, "Class must not be null");
  		Map<TypeVariable, Type> typeVariableMap = getTypeVariableMap(clazz);
  		Type rawType = getRawType(genericType, typeVariableMap);
  		return (rawType instanceof Class ? (Class) rawType : method.getReturnType());
  	}
docs: Determine the target type for the generic return type of the given method.
  @param method the method to introspect
  @param clazz the class to resolve type variables against
  @return the corresponding generic parameter or return type