--- OptionParser#summarize(to = [], width = @summary_width, max = width - 1, indent = @summary_indent)
    Puts option summary into to, and returns to.
    :Parameters:
      : to
        output destination, which must have method <<. Defaulted to [].
      : width
        width of left side. Defaulted to @summary_width
      : max
        maximum length allowed for left side. Defaulted to width - 1
      : indent
        indentation. Defaulted to @summary_indent
      : Block
        yields with each line if called as iterator.

