Minor patch convert_nx_to_pyg #280 (#281)

* nx_to_pyg bug fix #280

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* update changelog

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Arian Jamasb <arjamasb@gmail.com>

Author: 3 people

CHANGELOG.md

@@ -37,6 +37,9 @@
 #### Utils
 * [Improvement] - [#234](https://github.com/a-r-j/graphein/pull/234) - Adds `parse_aggregation_type` to retrieve aggregation functions.
 
+#### RNA
+* [Bugfix] - [#281](https://github.com/a-r-j/graphein/pull/234) - Bugfix for nx->PyG conversion for graphs containing edges without "kind" attributes. Contribution by @rg314.
+
 #### Constants
 * [Improvement] - [#234](https://github.com/a-r-j/graphein/pull/234) - Adds 1 to 3 mappings to `graphein.protein.resi_atoms`.
 

graphein/ml/conversion.py

@@ -305,13 +305,15 @@ def convert_nx_to_pyg(self, G: nx.Graph) -> Data:
             data["edge_index"] = edge_index
 
         # Split edge index by edge kind
-        kind_strs = np.array(list(map(lambda x: "_".join(x), data["kind"])))
+        kind_strs = np.array(
+            list(map(lambda x: "_".join(x), data.get("kind", [])))
+        )
         for kind in set(kind_strs):
             key = f"edge_index_{kind}"
             if key in self.columns:
                 mask = kind_strs == kind
                 data[key] = edge_index[:, mask]
-        if "kind" not in self.columns:
+        if "kind" not in self.columns and data.get("kind"):
             del data["kind"]
 
         # Convert everything possible to torch.Tensors