def parse_coord_args(x, y=0)
      if x.is_a?(String)
        x, y = *Axlsx::name_to_indices(x)
      end
      if x.is_a?(Cell)
        x, y = *x.pos
      end
      if x.is_a?(Array)
        x, y = *x
      end
      [x, y]
    end
handles multiple inputs for setting the position of a marker
@see Chart#start_at