type Fields … type Set … // String returns all fields listed as a human readable string. // Conveniently, exactly the format that ParseSelector takes. func (ls Set) String() string { … } // Has returns whether the provided field exists in the map. func (ls Set) Has(field string) bool { … } // Get returns the value in the map for the provided field. func (ls Set) Get(field string) string { … } // AsSelector converts fields into a selectors. func (ls Set) AsSelector() Selector { … }