hashmaps are incorrectly dumped in storage model

[cyberthirst]

pip show boa: 0.2.5
vyper --version: 0.4.0+commit.e9db8d9
python --version: 3.11.10

import boa

def test():
    code = """

h: HashMap[uint256, uint256]

@external
def foo():
    self.h[100000000] = 999
    self.h[64] = 2000
    """

    c = boa.loads(code)
    c.foo()
    print(c._storage.dump())

test()

output:

<storage: h={}>