def set_patch(self):
        """
        take xb from learner and convert to patch: [bs x seq_len x n_vars] -> [bs x num_patch x n_vars x patch_len]
        """
        xb_patch, num_patch = create_patch(self.xb, self.patch_len, self.stride)    # xb: [bs x seq_len x n_vars]
        # learner get the transformed input
        self.learner.xb = xb_patch                              # xb_patch: [bs x num_patch x n_vars x patch_len]           

        take xb from learner and convert to patch: [bs x seq_len x n_vars] -> [bs x num_patch x n_vars x patch_len]
        
PatchTST_self_supervised/src/callback/patch_mask.py