https://pytorch.org/docs/stable/torch.html?highlight=sparse_coo_tensor#torch.sparse_coo_tensor doesn't mention it and doesn't have examples.

SciPy mentions (https://docs.scipy.org/doc/scipy/reference/generated/scipy.sparse.coo_matrix.html) that the corresponding values are to be summed.

Would be useful for new users of PyTorch sparse package (like myself).