def each
      if @header
        @header.each{|k, v|
          value = @header[k]
          yield(k, value.empty? ? nil : value.join(", "))
        }
      end
    end
def each
      if @header
        @header.each{|k, v|
          value = @header[k]
          yield(k, value.empty? ? nil : value.join(", "))
        }
      end
    end
Iterates over the request headers