Have a look at docs 82 under the Variables paragraph.
Posting it here will mess up the format, but you’ll find some information about which internal LSTM parameters contain which part of the weight and bias matrices:

LSTM.weight_ih_l[k]  – the learnable input-hidden weights …

You can access these parameters directly via:
lstm = nn.LSTM(1, 1)
for name, _ in lstm.named_parameters():
    print(name)

> weight_ih_l0
weight_hh_l0
bias_ih_l0
bias_hh_l0

lstm.weight_ih_l0