Exception to be thrown when a self-adjoint RealLinearOperator is expected. Since the coefficients of the matrix are not accessible, the most general definition is used to check that A is not self-adjoint, i.e. there exist x and y such as | x' A y - y' A x | >= eps, where eps is a user-specified tolerance, and x' denotes the transpose of x. In the terminology of this exception, A is the "offending" linear operator, x and y are the first and second "offending" vectors, respectively.