code: def combine(specs):
          
          new_specs = {}
          for spec in specs:
              if new_specs.get(spec, None) is None:
                  new_specs[spec] = spec
              else:
                  new_specs[spec].add(spec)
          return list(new_specs.values())
docs: Combine package specifications' limitations.
  
          Args:
              specs (list of PackageSpec): the package specifications.
  
          Returns:
              list of PackageSpec: the new, merged list of PackageSpec.