The unity resolvent of a positive matrix. For an elementwise positive matrix \(X\), this atom represents \((I - X)^{-1}\),
and it enforces the constraint that the spectral radius of \(X\) is at most 1.

## Arguments

- X
An Expression or positive square matrix.

## Value

An Expression representing the unity resolvent of the input.

## Details

This atom is log-log convex.