old_contents: import numpy as np
  
  from .system import System
  
  
  class DipolarSystem(System):
      def setDefaultParams(self):
          self.params.setdefault("t", 1)
  
      def tunnelingRate(self, dr):
          t = self.get("t")
  
          dist3 = np.sum(dr ** 2, axis=3) ** (-3/2)
  
          # Orbital matrix
          # m = np.array([[1, 0], [0, -1]])
          m = np.array([-t])
  
          return t * m * dist3[:, :, :, None, None]
  
new_contents: import numpy as np
  
  from .system import System
  
  
  class DipolarSystem(System):
      def setDefaultParams(self):
          self.params.setdefault("t", 1)
  
      def tunnelingRate(self, dr):
          t = self.get("t")
  
          dist3 = np.sum(dr ** 2, axis=3) ** (-3/2)
  
          # Orbital matrix
          # m = np.array([[1, 0], [0, -1]])
          m = np.array([-t])
  
          return m * dist3[:, :, :, None, None]
  
subject: fix dipolar system