When the array is returned by yield, if I modify the array again will it change the value of the returned array?

Question

def path_yielder(t, value):
    """Yields all possible paths from the root of t to a node with the label value as a list."""
    def dfs(root, path):
        path += [root.label]
        backup = path[:]
        if len(path) and path[-1] == value:
            print("debug ", path)
            #yield path
            #yield path[:]
        if root != []:
            for branch in root.branches:
                **yield from dfs(branch, path)**
                path = backup[:]
    yield from dfs(t, [])

It's a problem in CS61A, When using generator recursion, the actual value returned by yield from is different from the value returned by base case using yield. The t argument is a data abstraction of Tree, I think it's doesn't matter.

>>> path_to_2 = path_yielder(t2, 2)
>>> sorted(list(path_to_2))
debug  [0, 2]
debug  [0, 2, 1, 2]
[[0, 2, 1, 2, 3], [0, 2, 1, 2, 3]]

# Error: expected
#     [[0, 2], [0, 2, 1, 2]]
# but got
#     [[0, 2, 1, 2, 3], [0, 2, 1, 2, 3]]

This is the actually execution result. On the line 7, I print the path array, result show that's [0,2] and[0, 2, 1, 2], but the yield from statement truly return [[0, 2, 1, 2, 3], [0, 2, 1, 2, 3]]. when I use return path[:], I pass the test. So, when the array is returned by yield, if I modify the array again, it will truly change the array I have returned, why? Hasn't this array been returned?

Is this a feature in python about arrays with the same address? The array I return has the same address as the real array. Changing one will change the other at the same time.