How do I verify this scaling relation?

I have a PDE as follows-

$ifrac{partial u}{partial xi} + frac{1}{2}frac{partial^2u}{partial tau^2} + |u|^2u = 0$

My book says that if $u(xi,tau)$ is a solution of the PDE, then $epsilon u(epsilon^2xi,epsilontau)$ is also a solution. Why is this true?