Activity for displaying messages preceded by the simulation time and the name of the arrival.
log_(.trj, message, level = 0)the trajectory object.
the message to display, accepts either a string or a callable object (a function) which must return a string.
debugging level. The message will be printed if, and only if,
the level provided is less or equal to the log_level defined in the
simulation environment (see simmer).
Returns the trajectory object.