code: @Override
      public JavaShellToolBuilder in(InputStream cmdIn, InputStream userIn) {
          this.cmdIn = cmdIn;
          this.userIn = userIn;
          return this;
      }
docs: Set the input channels.
  Default, if not set, {@code in(System.in, null)}.
  
  @param cmdIn source of command input
  @param userIn source of input for running user code, or {@code null} to
  be extracted from cmdIn
  @return the {@code JavaShellToolBuilder} instance