Why trace method used insted of script method in graph creation?

Why we use,

            trace = torch.jit.trace(model, args)
            graph = trace.graph

for creating graph for tensorboard insted of script method. Wont it be better for capturing networks, say with conditional statements in the forward?
Refr :

         https://github.com/pytorch/pytorch/blob/master/torch/utils/tensorboard/_pytorch_graph.py
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