code: def get_nac_eigendisplacements_along_dir(self, direction):
          
          versor = [i / np.linalg.norm(direction) for i in direction]
          for d, e in self.nac_eigendisplacements:
              if np.allclose(versor, d):
                  return e
  
          return None
docs: Returns the nac_eigendisplacements for the given direction (not necessarily a versor).
          None if the direction is not present or nac_eigendisplacements has not been calculated.
  
          Args:
              direction: the direction as a list of 3 elements
          Returns:
              the eigendisplacements as a numpy array of complex numbers with shape
              (3*len(structure), len(structure), 3). None if not found.