code: def test_unknown_command():
      t = make_tester()
      run(
          t,
          """\
  (b2db) xyzzy
  Unknown command: xyzzy
  (b2db) gnusto rezrov
  Unknown command: gnusto
  (b2db) quit
  """,
      )
  
      t.cleanup()
  
imports: import BoostBuild
  import TestCmd
  import re
label_desc: Use image node_id 19 for calling a global function with example usage: test_unknown_command() without return types