code: def get_subset_in_chemsys(self, chemsys: List[str]):
          
          chemsys = set(chemsys)
          if not chemsys.issubset(self.chemsys):
              raise ValueError("%s is not a subset of %s" % (chemsys,
                                                             self.chemsys))
          subset = set()
          for e in self.entries:
              elements = [sp.symbol for sp in e.composition.keys()]
              if chemsys.issuperset(elements):
                  subset.add(e)
          return EntrySet(subset)
docs: Returns an EntrySet containing only the set of entries belonging to
          a particular chemical system (in this definition, it includes all sub
          systems). For example, if the entries are from the
          Li-Fe-P-O system, and chemsys=["Li", "O"], only the Li, O,
          and Li-O entries are returned.
  
          Args:
              chemsys: Chemical system specified as list of elements. E.g.,
                  ["Li", "O"]
  
          Returns:
              EntrySet