docs: def get_cost_per_kg(self, comp):
          """
          Get best estimate of minimum cost/kg based on known data
  
          Args:
              comp:
                  Composition as a pymatgen.core.structure.Composition
          Returns:
              float of cost/kg
          """
          comp = comp if isinstance(comp, Composition) else Composition(comp)
          return self.get_cost_per_mol(comp) / (
              comp.weight.to("kg") * const.N_A)