Traverse initiates a DAG traversal with the given options starting at the given root.

BFS defines breadth-first order.

DFSPost defines depth-first post-order.

DFSPre defines depth-first pre-order.

Options specifies a series of traversal options.

State is a current traversal state.

ErrFunc is provided to handle problems when walking to the Node.

Func is the type of the function called for each dag.Node visited by Traverse.

Order is an identifier for traversal algorithm orders.