Can anyone please help me with this question, I am really confused...

Show that the function g(z)=Im z is not differentiable anywhere using the definition of f to be differentiable at a point 'z' . where f:u (tending to)Complex numbers.

for f to be differentiable then the limit of

lim [f(z) - f(z0)]/(z-z0) (z tending to z0) must exist. But how so I show that this is not the case with g(z)=Im z ...the imaginary part?

Thanks