code: def compute_eigh(self):
          
          self.eigh1 = _SHGrid.from_array(_np.zeros_like(self.vxx.data),
                                          grid='DH')
          self.eigh2 = _SHGrid.from_array(_np.zeros_like(self.vxx.data),
                                          grid='DH')
          self.eighh = _SHGrid.from_array(_np.zeros_like(self.vxx.data),
                                          grid='DH')
  
          for i in range(self.nlat):
              for j in range(self.nlon):
                  a = _np.array([[self.vxx.data[i, j],
                                  self.vxy.data[i, j]],
                                 [self.vyx.data[i, j],
                                  self.vyy.data[i, j]]])
  
                  eigs = _eigvalsh(a)
  
                  self.eigh1.data[i, j] = eigs[1]
                  self.eigh2.data[i, j] = eigs[0]
  
                  if abs(eigs[0]) >= abs(eigs[1]):
                      self.eighh.data[i, j] = eigs[0]
                  else:
                      self.eighh.data[i, j] = eigs[1]
docs: Compute the two horizontal eigenvalues of the tensor (eigh1, and
          eigh2), as well as the combined maximum absolute value of the two
          (eighh).