[Dev] Flow exception

[ocots]

If we make using OrdinaryDiffEq but then we do not call Flow with the right arguments, then it is written to import OrdinaryDiffEq. This should not happen.

[ocots]

See this: https://github.com/control-toolbox/CTModels.jl/blob/51978e74e7042e4688764d4c9e2a1d4803d2bc1b/src/CTModels.jl#L182-L185

I need to provide the same arguments as the method in the extension, except for the type of the first argument: provide an abstract supertype.