code: def render(self, rect, data):
          
          num_elements = len(self.elements)
          col_width = (rect.w-self.margin*(num_elements-1)) / float(num_elements)
          x = rect.x
          for element in self.elements:
              if element is not None:
                  element.render(datatypes.Rectangle(
                          x, rect.y, col_width, rect.h
                          ), data)
              x += col_width + self.margin
docs: Draws the columns.