docs: def get_lowest_decomposition(self, composition):
          """
          Get the decomposition leading to lowest cost
  
          Args:
              composition:
                  Composition as a pymatgen.core.structure.Composition
          Returns:
              Decomposition as a dict of {Entry: amount}
          """
  
          entries_list = []
          elements = [e.symbol for e in composition.elements]
          for i in range(len(elements)):
              for combi in itertools.combinations(elements, i + 1):
                  chemsys = [Element(e) for e in combi]
                  x = self.costdb.get_entries(chemsys)
                  entries_list.extend(x)
          try:
              pd = PhaseDiagram(entries_list)
              return pd.get_decomposition(composition)
          except IndexError:
              raise ValueError("Error during PD building; most likely, "
                               "cost data does not exist!")