code: func MappingFuncFor(context ...map[string]string) func(string) string {
  	return func(input string) string {
  		for _, vars := range context {
  			val, ok := vars[input]
  			if ok {
  				return val
  			}
  		}
  
  		return syntaxWrap(input)
  	}
  }
docs: // MappingFuncFor returns a mapping function for use with Expand that
  // implements the expansion semantics defined in the expansion spec; it
  // returns the input string wrapped in the expansion syntax if no mapping
  // for the input is found.