pm.traceplot returns an array of matplotlib axes objects, and you can call set_xlim on them.
axes = pm.traceplot()
axes[0,0].set_xlim(a,b)
pm.traceplot returns an array of matplotlib axes objects, and you can call set_xlim on them.
axes = pm.traceplot()
axes[0,0].set_xlim(a,b)