'Determine stability based on model coefficients
Parameters
verbose : bool
Print eigenvalues of the VAR(1) companion
Notes
Checks if det(I - Az) = 0 for any mod(z) <= 1, so all the eigenvalues of
the companion matrix must lie outside the unit circle'

def is_stable(self, verbose=False):

    return is_stable(self.coefs, verbose=verbose)
