Can we simulate all dynamic graph with static graph?

1

in sequence model (such as recurrent neural network)

Sequence model should be a dynamic graph due to the dynamic input length and output length. Right?
In traditional implementation of static graph, we always fix the input length to make it a static graph.

In the example of dynamic layers 

    def forward(self, x):
        h_relu = self.input_linear(x).clamp(min=0)
        for _ in range(random.randint(0, 3)):
            h_relu = self.middle_linear(h_relu).clamp(min=0)
        y_pred = self.output_linear(h_relu)
        return y_pred

I think a static graph can also do this. For example, first create a 4-layer h_relu, then random.randint(0, 3) as input instead of graph structure, which dynamically disable the h_relu layer.

in tree-based model (such as recursive neural network)