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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def prune(self):
 """ On a subtree where the root node's s_center is empty, return a new subtree with no empty s_centers. """

        if not self[0] or not self[1]:    # if I have an empty branch
            direction = not self[0]       # graft the other branch here
            #if trace:
            #    print('Grafting {} branch'.format(
            #       'right' if direction else 'left'))

            result = self[direction]
            #if result: result.verify()
            return result
        else:
            # Replace the root node with the greatest predecessor.
            heir, self[0] = self[0].pop_greatest_child()
            #if trace:
            #    print('Replacing {} with {}.'.format(
            #        self.x_center, heir.x_center
            #        ))
            #    print('Removed greatest predecessor:')
            #    self.print_structure()

            #if self[0]: self[0].verify()
            #if self[1]: self[1].verify()

            # Set up the heir as the new root node
            (heir[0], heir[1]) = (self[0], self[1])
            #if trace: print('Setting up the heir:')
            #if trace: heir.print_structure()

            # popping the predecessor may have unbalanced this node;
            # fix it
            heir.refresh_balance()
            heir = heir.rotate()
            #heir.verify()
            #if trace: print('Rotated the heir:')
            #if trace: heir.print_structure()
            return heir