human
Complete the below
def _SetMustSplitOnFirstLeaf(node):

    ''''Set the "must split" annotation on the first leaf node.'
    '''

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Can you provide a the Python code you requested?
assistant
#Here is the Python code you requested.
    def FindFirstLeaf(node):
        if isinstance(node, pytree.Leaf):
            return node
        return FindFirstLeaf(node.children[0])
    pytree_utils.SetNodeAnnotation(FindFirstLeaf(node), pytree_utils.Annotation.MUST_SPLIT, True)