  This paper studies the celebrated Kuramoto-Sakaguchi model of coupled
oscillators adopting two recent concepts. First, we consider
appropriately-defined subsets of the $n$-torus called winding cells. Second, we
analyze the semicontractivity of the model, i.e., the property that the
distance between trajectories decreases when measured according to a seminorm.
  This paper establishes the local semicontractivity of the Kuramoto-Sakaguchi
model, which is equivalent to the local contractivity for the reduced model.
The reduced model is defined modulo the rotational symmetry. The domains where
the system is semicontracting are convex phase-cohesive subsets of winding
cells. Our sufficient conditions and estimates of the semicontracting domains
are less conservative and more explicit than in previous works. Based on
semicontraction on phase-cohesive subsets, we establish the "at most
uniqueness" of synchronous states within these domains, thereby characterizing
the multistability of this model.
