Python homework:how to write and test a _swap method for the linked Deque.

def _swap(self, l, r):

""" -------------------------------------------------------

Swaps two pointers. Use: self._swap(self, l, r):

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Preconditions:

l - a pointer to a deque node (_DequeNode)

r - a pointer to a deque node (_DequeNode)

Postconditions: l has taken the place of r, r has taken the place of l _front and _rear are updated as appropriate

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"""

assert l is not None and r is not None, "nodes to swap cannot be None"

please give a thinking of this, I don;t know which method to use.