add datamodule

tests/test_datamodule.py

@@ -0,0 +1,13 @@
+from ThermalSolver.data_module import GraphDataModule
+
+def test_graph_data_module():
+    data_module = GraphDataModule(
+    hf_repo="SISSAmathLab/thermal-conduction",
+    split_name="pytest",
+    train_size=0.8,
+    val_size=0.1,
+    test_size=0.1,
+    batch_size=32,
+    )
+    data_module.prepare_data()
+    data_module.setup("fit")