def row(index, &block)
      if block_given?
        rows.fetch(index) { return self }.each(&block)
        self
      else
        rows.fetch(index) { return nil }
      end
    end
def row(index, &block)
      if block_given?
        rows.fetch(index) { return self }.each(&block)
        self
      else
        rows.fetch(index) { return nil }
      end
    end
Return a row number at the index of the table as an Array.
 When a block is given, the elements of that Array are iterated over.

 @example
   rows  = [['a1', 'a2'], ['b1', 'b2']]
   table = TTY::Table.new rows: rows
   table.row(1) { |row| ... }

 @param [Integer] index

 @yield []
   optional block to execute in the iteration operation

 @return [self]

 @api public