def duplicate_transition_ignore(old_transition, new_transition):
    """
    Default function for handling duplicate transitions in finite
    state machines. This implementation ignores the occurrence.

    See the documentation of the ``on_duplicate_transition`` parameter
    of :class:`FiniteStateMachine`.

    INPUT:

    - ``old_transition`` -- A transition in a finite state machine.

    - ``new_transition`` -- A transition, identical to ``old_transition``,
      which is to be inserted into the finite state machine.

    OUTPUT:

    The same transition, unchanged.

    EXAMPLES::

        sage: from sage.combinat.finite_state_machine import duplicate_transition_ignore
        sage: from sage.combinat.finite_state_machine import FSMTransition
        sage: duplicate_transition_ignore(FSMTransition(0, 0, 1),
        ....:                             FSMTransition(0, 0, 1))
        Transition from 0 to 0: 1|-
    """
    return old_transition