code: def orientation(self):
          
  
          a, b, b, c = self.covariance.flat
          if a < 0 or c < 0:    # negative variance
              return np.nan * u.rad  # pragma: no cover
          return 0.5 * np.arctan2(2. * b, (a - c))
docs: The angle in radians between the ``x`` axis and the major axis
          of the 2D Gaussian function that has the same second-order
          moments as the source.  The angle increases in the
          counter-clockwise direction.