trex_cmd.add_if(u"--astf", osi_layer == u"L7")
# OptionString does not create double space if extra is empty.
trex_cmd.add(f"{Constants.TREX_EXTRA_CMDLINE}")
trex_cmd.add_if(u"--astf", osi_layer == u"L7")
# OptionString does not create double space if extra is empty.
trex_cmd.add(f"{Constants.TREX_EXTRA_CMDLINE}")