code: def header(self, item0, *items):
          
          self.txt(item0)
          at_x = None
          for item in items:
              if at_x is None:
                  at_x = item
              else:
                  self.txt(item, at_x=at_x)
                  at_x = None
docs: print string item0 to the current position and next strings to defined positions
          example: .header("Name", 75, "Quantity", 100, "Unit")