template/template.go
func (te Expander) Funcs(fm text_template.FuncMap) {
	for k, v := range fm {
		te.funcMap[k] = v
	}
}
func (te Expander) Funcs(fm text_template.FuncMap) {
	for k, v := range fm {
		te.funcMap[k] = v
	}
}
// Funcs adds the functions in fm to the Expander's function map.
// Existing functions will be overwritten in case of conflict.