mdp.Flow:
A 'Flow' is a sequence of nodes that are trained and executed
together to form a more complex algorithm.
mdp.CheckpointFlow:
Subclass of Flow class that allows user-supplied checkpoint functions
to be executed at the end of each phase, for example to
save the internal structures of a node for later analysis.
mdp.OnlineFlow:
An 'OnlineFlow' is a sequence of nodes that are trained online and executed
together to form a more complex algorithm.
mdp.CircularOnlineFlow:
A 'CircularOnlineFlow' is a cyclic sequence of online/non-trainable nodes that are trained and executed
together to form a more complex algorithm.
mdp.Node:
A `Node` is the basic building block of an MDP application.
mdp.Cumulator:
A specialized version of `VariadicCumulator` which only
fills the field ``self.data``.
unreachable.Cumulator
mdp.ClassifierCumulator:
A ClassifierCumulator is a Node whose training phase simply collects
all input data and labels.
mdp.OnlineNode:
An online Node (OnlineNode) is the basic building block of
an online MDP application.