# For Stanza trees in HW10 Task 5
#   Sandiway Fong, University of Arizona

def subtree(t):
    """generator for subtrees of t"""
    for i in range(len(t.children)):
        yield t.children[i]

def subtrees(t):
    """recursively generate all subtrees of t"""
    for t2 in subtree(t):
        yield t2
        yield from subtrees(t2)

def plabel(t):
    if t.label in verbtags and t.children[0].label in verbforms:
        return 'break'
    else:
        return t.label