code: func (t Type) IsUnion() bool {
  	if t.IsJSONType() {
  		return false
  	}
  	return strings.Index(t.TypeString(), "|") > 0
  }
docs: // IsUnion checks if a type is Union type
  // see http://docs.raml.org/specs/1.0/#raml-10-spec-union-types