docs: separated docstring

src/anemoi/models/layers/conv.py

@@ -76,7 +76,9 @@ def aggregate(self, edges_new: Tensor, edge_index: Adj, dim_size: Optional[int]
 
 
 class GraphTransformerConv(MessagePassing):
-    """Message passing part of graph transformer operator from 'Masked Label Prediction: Unified Message Passing Model for Semi-Supervised Classification'
+    """Message passing part of graph transformer operator. 
+    
+    Adapted from 'Masked Label Prediction: Unified Message Passing Model for Semi-Supervised Classification'
     (https://arxiv.org/abs/2009.03509)
     """