
"""
...
"""
process_coarse!(problem, level) = nothing

"""
...
"""
process_fine!(problem, level) = nothing

"""
...
"""
process_uncoarse!(problem, level) = nothing

"""
...
"""
coarsen!(problem, level) = nothing

"""
...
"""
uncoarsen!(problem, level) = nothing

"""
...
"""
doinitial(problem, level) = false

"""
...
"""
initial!(problem, level) = nothing

"""
...
"""
process_initial!(problem, level) = nothing

"""
...
"""
precycle!(problem, level) = nothing

"""
...
"""
postcycle!(problem, level) = nothing

"""
...
"""
preprocessing!(problem, level) = nothing

"""
...
"""
postprocessing!(problem, level) = nothing

