# File lib/active_support/core_ext/array/grouping.rb, line 19
  def in_groups_of(number, fill_with = nil)
    if fill_with == false
      collection = self
    else
      # size % number gives how many extra we have;
      # subtracting from number gives how many to add;
      # modulo number ensures we don't add group of just fill.
      padding = (number - size % number) % number
      collection = dup.concat([fill_with] * padding)
    end

    if block_given?
      collection.each_slice(number) { |slice| yield(slice) }
    else
      groups = []
      collection.each_slice(number) { |group| groups << group }
      groups
    end
  end