function _matrixNormTwo (x) {
      // norm(x) = sqrt( max eigenvalue of A*.A)
      const sizeX = x.size()
      if (sizeX[0] !== sizeX[1]) {
        throw new RangeError('Invalid matrix dimensions')
      }
      const tx = ctranspose(x)
      const squaredX = multiply(tx, x)
      const eigenVals = eigs(squaredX).values.toArray()
      const rho = eigenVals[eigenVals.length - 1]
      return abs(sqrt(rho))
    }
Calculate the norm L2 for a matrix
@param {Matrix} x
@returns {number} Returns the norm
@private