Update exp_smooth.py

Author: jwdink

torchcast/exp_smooth/exp_smooth.py

@@ -36,9 +36,8 @@ def __init__(self,
         self.smoothing_matrix = smoothing_matrix.set_id('smoothing_matrix')
 
     def initial_covariance(self, inputs: dict, num_groups: int, num_times: int, _ignore_input: bool = False) -> Tensor:
-        # initial covariance is always zero. this will be replaced by the 1-step-ahead covariance in the first call to
-        # predict
-        m = list(self.processes)[0].initial_mean # get a parameter, any parameter, to get device
+        # initial covariance is always zero. this will be replaced by the 1-step covariance in the first call to predict
+        m = list(self.processes.values())[0].initial_mean  # get a parameter, any parameter, to get device
         return torch.zeros((num_groups, num_times, self.state_rank, self.state_rank), dtype=m.dtype, device=m.device)
 
     def _mask_mats(self,