Work around lack of inheritance in TorchScript.

Author: lohedges

src/sire/qm/_emle.py

@@ -156,6 +156,7 @@ def emle(
         )
 
     try:
+        import torch as _torch
         from emle.models import EMLE as _EMLE
 
         has_model = True
@@ -181,7 +182,17 @@ def emle(
         raise ValueError("Unable to select 'qm_atoms' from 'mols'")
 
     if has_model:
-        if not isinstance(calculator, (_EMLECalculator, _EMLE)):
+        # EMLECalculator.
+        if isinstance(calculator, _EMLECalculator):
+            pass
+        # EMLE model. Note that TorchScript doesn't support inheritance, so
+        # we need to check whether this is a torch.nn.Module and whether it
+        # has the "_is_emle" attribute, which is added to all EMLE models.
+        elif isinstance(calculator, _torch.nn.Module) and hasattr(
+            calculator, "_is_emle"
+        ):
+            pass
+        else:
             raise TypeError(
                 "'calculator' must be a of type 'emle.calculator.EMLECalculator' or 'emle.models.EMLE'"
             )