Seen values for mutable structures

[Jaymon]

        def foo():
            d = {}
            for i in range(5):
                d[i] = i
                yield d

        pout.v(foo())

Would result in:

foo() = ... (5)
    (
        0: dict (1)
            {
                0: 0
            },
        1: <dict (2) at 0x103317c00>,
        2: <dict (3) at 0x103317c00>,
        3: <dict (4) at 0x103317c00>,
        4: <dict (5) at 0x103317c00>
    )

Notice how the dictionary count changes in indexes 1-4 but it doesn't display them because the same dictionary has been mutated but pout has already "seen" the dictionary so it sends it through Value.seen_value instead of generating the string value again.

I'm not completely sure how to fix this. I can save the count value and add a check to show regenerate the value if the count has changed, but that doesn't completely fix the problem.