code: func HashSchema(schema *Schema) SchemaSetFunc {
  	return func(v interface{}) int {
  		var buf bytes.Buffer
  		SerializeValueForHash(&buf, v, schema)
  		return hashcode.String(buf.String())
  	}
  }
docs: // HashSchema hashes values that are described using a *Schema. This is the
  // default set implementation used when a set's element type is a single
  // schema.