How to define *complex* symbolic variables

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Hello,

I am quite new with SageMath, and I don't succeed in defining complex symbolic variables.

In the following example, SageMath seems to compute as if the variables were real (and not complex) :

var('w_2')
T=Matrix([[0, w_2], [0,0]])
S=T*(T.H)
S.eigenvalues()

The output of this command is

[w_2^2, 0]

whereas the expected result was

[norm(w_2), 0]

How can I tell SageMath that my symbolic variables are complex ones ?

Thanks in advance for your help !