old_contents: from .gravity import Gravity, Production, Attraction, Doubly
  from .utils import CPC, sorensen, smrse, 
  from .vec_SA import VecMoran as Moran_Vector
  from .dispersion import import phi_disp, alpha_disp
  
new_contents: from .gravity import Gravity, Production, Attraction, Doubly
  from .utils import CPC, sorensen, smrse, 
  from .vec_SA import VecMoran as Moran_Vector
  from .dispersion import phi_disp, alpha_disp
  
subject: remove double import