<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _occurrence_intersection(occ_P, occ_Q):
 """Computes the intersection between two occurrences. Parameters occ_P : list of tuples (onset, midi) pairs representing the reference occurrence. occ_Q : list second list of (onset, midi) tuples Returns ------- S : set Set of the intersection between occ_P and occ_Q. """

    set_P = set([tuple(onset_midi) for onset_midi in occ_P])
    set_Q = set([tuple(onset_midi) for onset_midi in occ_Q])
    return set_P & set_Q