Dependencies

def getDependentNodes(node, mask = nuke.INPUTS | nuke.HIDDEN_INPUTS | nuke.EXPRESSIONS):
    stack = node.dependencies(mask)
    seen = set()
    depNodes = [node]
    while stack:
        node = stack.pop()
        if node in seen:
            continue
        depNodes.append(node)
        seen.add(node)
        stack.extend(node.dependencies(mask))
    return depNodes

def cleanNodes(writeNode):
    depNodes = getDependentNodes(writeNode)
    for n in nuke.allNodes():
        if n not in depNodes:
            nuke.delete(n)

print getDependentNodes(t)