def extend(header, extensions)
      join(
        header,
        extensions.map { |extension| Function.extract_value(extension, self) }
      )
    end
def extend(header, extensions)
      join(
        header,
        extensions.map { |extension| Function.extract_value(extension, self) }
      )
    end
Extend a tuple with function results

 @example
   new_tuple = tuple.extend(header, [func1, func2])

 @param [Header] header
   the attributes to include in the tuple
 @param [Array<Object>] extensions
   the functions to extend the tuple with

 @return [Tuple]

 @api public