checking user defined types

[Luis Solís]

I have defined a class Myclass

I instanciate the class and I use it in a function, and I could like check
the argument type in the function, but this code don't works

func (xMyclass,..):
    if  type(xMyclass) is type(Myclass): ...

then I must create a new object of the class and then

if type(xMyclass) is type(Myclass()):

this solution has the problem when Myclass has a complex constructor.
Do you known another solution ?

Thanks in advance