using OrdinaryDiffEq

# Auto callback merging

do_nothing = DiscreteCallback(
     (u,t,integrator) -> true,
     integrator -> nothing
 )
problem = ODEProblem(
   (u,p,t)->-u,
   1.0, (0.0,1.0),
   callback = do_nothing
)
solve(
   problem, Euler(),
   dt = 0.1,
   callback = do_nothing
)
