"""
    graph_properties(graph::DAG)

Return the graph's properties, a named tuple with fields `.data`, `.compute_effort`, `.compute_intensity`, `.nodes` (number of nodes) and `.edges` (number of edges).
"""
function graph_properties(graph::DAG)
    # make sure the graph is fully generated
    apply_all!(graph)

    d = 0
    ce = 0
    ed = 0
    for node in graph.nodes
        d += data(node.task) * length(node.parents)
        ce += compute_effort(node.task)
        ed += length(node.parents)
    end

    ci = ce / d

    result = (
        data = d,
        compute_effort = ce,
        compute_intensity = ci,
        nodes = length(graph.nodes),
        edges = ed,
    )
    return result
end

"""
    get_exit_node(graph::DAG)

Return the graph's exit node. This assumes the graph only has a single exit node. If the graph has multiple exit nodes, the one encountered first will be returned.
"""
function get_exit_node(graph::DAG)
    for node in graph.nodes
        if (is_exit_node(node))
            return node
        end
    end
    @assert false "The given graph has no exit node! It is either empty or not acyclic!"
end