def change_font_size(font_size = 10)
      validate_worksheet
      raise 'Argument must be a number' unless font_size.is_a?(Integer) || font_size.is_a?(Float)

      font = get_cell_font.dup
      font.set_size(font_size)
      update_font_references(font)
    end
def change_font_size(font_size = 10)
      validate_worksheet
      raise 'Argument must be a number' unless font_size.is_a?(Integer) || font_size.is_a?(Float)

      font = get_cell_font.dup
      font.set_size(font_size)
      update_font_references(font)
    end
Changes font size of cell