Accessing the "Echelon basis matrix" of kernel of a Matrix

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For any matrix A when we type

A.kernel()

It returns

 A.kernel()
Free module of degree 45 and rank 12 over Integer Ring
Echelon basis matrix:`[ 1  0 -1][ 0  1  2][ 0  0  0]`

How to I access this Echelon basis matrix directly?

I have tried this

A.kernel.echelon_form()

but it says

TypeError: echelon_form() takes at least 2 arguments (1 given)