Add M() to docstring
@@ -1267,7 +1267,7 @@ class LangevinSplittingIntegrator(ThermostatedIntegrator):
Parameters
----------
step_string : str
- R, O, V, or Vn (where n is a nonnegative integer specifying force group)
+ R, O, V, M(, ), or Vn (where n is a nonnegative integer specifying force group)
measure_shadow_work : bool
Whether the steps should measure shadow work
measure_heat : bool
