class Asciidoctor::Reader

advance to the next line and process it.
invocation of Reader#read_line or nil if the Reader should drop the line,
Returns The String line the Reader should make available to the next

the line unmodified.
by incrementing the look_ahead counter and returns
By default, this method marks the line as processed

Internal: Processes a previously unvisited line

def process_line line
  @look_ahead += 1 if @process_lines
  line
end