Takes the most recent command from the undo list and undoes it.
Derived from mel command maya.cmds.undo
Example:
import pymel.core as pm
# In this particular example, each line needs to be executed
# separately one after the other. Executing lines separately
# guaranties that commands are properly registered in the undo
# stack.
pm.polyCube()
# Result: [nt.Transform(u'pCube1'), nt.PolyCube(u'polyCube1')] #
pm.polySphere()
# Result: [nt.Transform(u'pSphere1'), nt.PolySphere(u'polySphere1')] #
pm.undo()
# Undo: pm.polySphere()
#
pm.undo()
# Undo: pm.polyCube()
#