def trace(bitmap = nil, params = nil, &block)
      if block_given?
        do_trace(bitmap || @bitmap, params || @params, &block)
      else
        do_trace(bitmap || @bitmap, params || @params)
      end
    end
def trace(bitmap = nil, params = nil, &block)
      if block_given?
        do_trace(bitmap || @bitmap, params || @params, &block)
      else
        do_trace(bitmap || @bitmap, params || @params)
      end
    end
Trace the given +bitmap+

 ==== Attributes

 * +bitmap+ - an instance of Potracer::Bitmap. If not given the +@bitmap+
   is used.
 * +params+ - an instance of Potracer::Params. If not given +@params+ is
   used.
 * +block+ - optional block called to report trace progress