code: public void visitLineNumber(int line, Label start) {
          if (mv != null) {
              mv.visitLineNumber(line, start);
          }
      }
docs: Visits a line number declaration.
  
  @param line
  a line number. This number refers to the source file from
  which the class was compiled.
  @param start
  the first instruction corresponding to this line number.
  @throws IllegalArgumentException
  if <tt>start</tt> has not already been visited by this
  visitor (by the {@link #visitLabel visitLabel} method).