# File lib/pry/indent.rb, line 194
    def indentation_delta(tokens)

      # We need to keep track of whether we've seen a "for" on this line because
      # if the line ends with "do" then that "do" should be discounted (i.e. we're
      # only opening one level not two) To do this robustly we want to keep track
      # of the indent level at which we saw the for, so we can differentiate
      # between "for x in [1,2,3] do" and "for x in ([1,2,3].map do" properly
      seen_for_at = []

      # When deciding whether an "if" token is the start of a multiline statement,
      # or just the middle of a single-line if statement, we just look at the
      # preceding token, which is tracked here.
      last_token, last_kind = [nil, nil]

      # delta keeps track of the total difference from the start of each line after
      # the given token, 0 is just the level at which the current line started for
      # reference.
      remove_before, add_after = [0, 0]

      # If the list of tokens contains a matching closing token the line should
      # not be indented (and thus we should return true).
      tokens.each do |token, kind|
        is_singleline_if  = (SINGLELINE_TOKENS.include?(token)) && end_of_statement?(last_token, last_kind)
        is_optional_do = (token == "do" && seen_for_at.include?(add_after - 1))

        last_token, last_kind = token, kind unless kind == :space
        next if IGNORE_TOKENS.include?(kind)

        track_module_nesting(token, kind)

        seen_for_at << add_after if OPTIONAL_DO_TOKENS.include?(token)

        if kind == :delimiter
          track_delimiter(token)
        elsif OPEN_TOKENS.keys.include?(token) && !is_optional_do && !is_singleline_if
          @stack << token
          add_after += 1
        elsif token == OPEN_TOKENS[@stack.last]
          popped = @stack.pop
          track_module_nesting_end(popped)
          if add_after == 0
            remove_before += 1
          else
            add_after -= 1
          end
        elsif MIDWAY_TOKENS.include?(token)
          if add_after == 0
            remove_before += 1
            add_after += 1
          end
        end
      end

      return [remove_before, add_after]
    end