code: def _scaling_func_list(bdry_fracs, exponent):
      
      def scaling(factor):
          def scaling_func(x):
              return x * factor
          return scaling_func
  
      func_list = []
      for frac_l, frac_r in bdry_fracs:
          func_list_entry = []
          if np.isclose(frac_l, 1.0):
              func_list_entry.append(None)
          else:
              func_list_entry.append(scaling(frac_l ** (1 / exponent)))
  
          if np.isclose(frac_r, 1.0):
              func_list_entry.append(None)
          else:
              func_list_entry.append(scaling(frac_r ** (1 / exponent)))
  
          func_list.append(func_list_entry)
      return func_list
docs: Return a list of lists of scaling functions for the boundary.