# Compute the inverse of a 2-form

I have a nondegenerate (0,2)-tensor `omega`

on a manifold which is not a metric and I would like to compute its 'inverse', which is a (2,0)-tensor.

I tried `omega[:].inverse()`

but I get the following error `'ChartFunctionRing_with_category' object has no attribute 'fraction_field'`

. This worked for me in older versions of Sagemath (I think it was 7.4).