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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def is_in(property_name, set_values, *, present_optional=False, message=None):
 """Returns a Validation that checks that a value is contained within a given set."""

    def check(val):
      """Checks that a value is contained within a scope-enclosed set."""
      if val is None:
        return present_optional
      else:
        return val in set_values

    return Validation(check, property_name, message)