Final answer:
The output of the code is 'list'. The code appends [4, 5, 6] to the existing list [1, 2, 3].
Step-by-step explanation:
The output of this code would be:
list
Since the code is iterating over the dictionary using a for loop, the only key in the dictionary is 'list'. Therefore, the output will be:
list
The code appends the list [4, 5, 6] to the existing list [1, 2, 3], resulting in [1, 2, 3, [4, 5, 6]].