Python 3.11 compatibility + Test on Python3.11 (#1876)

* GHA: Run tests on Python3.11
* Fixes related to Python3.11 changes to enums (https://docs.python.org/3/whatsnew/3.11.html#enum)
* Fix unreliable string `is` comparison

Author: dweindl

.github/workflows/test_python_ver_matrix.yml

@@ -24,7 +24,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [3.8, 3.9, '3.10']
+        python-version: [3.8, 3.9, '3.10', '3.11']
         experimental: [false]
 
     steps:

python/sdist/amici/ode_export.py

@@ -1872,7 +1872,7 @@ def _derivative(self, eq: str, var: str, name: str = None) -> None:
             cv for cv in ['w', 'tcl']
             if var_in_function_signature(eq, cv)
                and cv not in self._lock_total_derivative
-               and var is not cv
+               and var != cv
                and min(self.sym(cv).shape)
                and (
                        (eq, var) not in ignore_chainrule
@@ -3070,7 +3070,7 @@ def _write_model_header_cpp(self) -> None:
                 self._get_symbol_name_initializer_list('y'),
             'OBSERVABLE_TRAFO_INITIALIZER_LIST':
                 '\n'.join(
-                    f'ObservableScaling::{trafo}, // y[{idx}]'
+                    f'ObservableScaling::{trafo.value}, // y[{idx}]'
                     for idx, trafo in enumerate(
                         self.model.get_observable_transformations()
                     )

python/sdist/amici/ode_model.py

@@ -297,12 +297,15 @@ class Observable(ModelQuantity):
 
     _measurement_symbol: Union[sp.Symbol, None] = None
 
-    def __init__(self,
-                 identifier: sp.Symbol,
-                 name: str,
-                 value: sp.Expr,
-                 measurement_symbol: Optional[sp.Symbol] = None,
-                 transformation: Optional[ObservableTransformation] = 'lin'):
+    def __init__(
+            self,
+            identifier: sp.Symbol,
+            name: str,
+            value: sp.Expr,
+            measurement_symbol: Optional[sp.Symbol] = None,
+            transformation: Optional[
+                ObservableTransformation] = ObservableTransformation.LIN
+    ):
         """
         Create a new Observable instance.