code: def combine_type(observations):
      
      assert len(observations) > 0
      if len(observations) == 1:
          return observations[0]
      else:
          if simplify:
              simplify_for_Union(observations)
          return Union[tuple(observations)]
docs: Combines a list of types into one.
      Basically these are combined into a Union with some
      additional unification effort (e.g. can apply PEP 484 style numeric tower).