tff.framework.transform_preorder

Walks the AST of comp preorder, calling transform on the way down.

tff.framework.transform_preorder(
    comp: tff.framework.ComputationBuildingBlock,
    transform: Callable[[building_blocks.ComputationBuildingBlock], TransformReturnType]
) -> tff.framework.ComputationBuildingBlock

Notice that this function will stop walking the tree when its transform function modifies a node; this is to prevent the caller from unexpectedly kicking off an infinite recursion. For this purpose the transform function must identify when it has transformed the structure of a building block; if the structure of the building block is modified but False is returned as the second element of the tuple returned by transform, transform_preorder may result in an infinite recursion.

comp Instance of building_blocks.ComputationBuildingBlock to be transformed in a preorder fashion.
transform Transform function to be applied to the nodes of comp. Must return a two-tuple whose first element is a building_blocks.ComputationBuildingBlock and whose second element is a Boolean. If the computation which is passed to comp is returned in a modified state, must return True for the second element. This Boolean controls whether or not to stop traversing the tree under comp; if this Bool is True, transform_preorder will not traverse this subtree.

A two-tuple, whose first element is modified version of comp, and whose second element is a Boolean indicating whether comp was transformed during the walk.

TypeError If the argument types don't match those specified above.