Fix TypeError in JAXProblem._get_measurements

Use pandas 2.x & 3.x compatible check for string dtypes.

Fixes #3120.

Author: dweindl

python/sdist/amici/jax/petab.py

@@ -286,13 +286,9 @@ def _get_measurements(
         for col in [petab.OBSERVABLE_PARAMETERS, petab.NOISE_PARAMETERS]:
             n_pars[col] = 0
             if col in self._petab_problem.measurement_df:
-                if np.issubdtype(
-                    self._petab_problem.measurement_df[col].dtype, np.number
+                if pd.api.types.is_string_dtype(
+                    self._petab_problem.measurement_df[col].dtype
                 ):
-                    n_pars[col] = 1 - int(
-                        self._petab_problem.measurement_df[col].isna().all()
-                    )
-                else:
                     n_pars[col] = (
                         self._petab_problem.measurement_df[col]
                         .str.split(petab.C.PARAMETER_SEPARATOR)
@@ -303,6 +299,10 @@ def _get_measurements(
                         )
                         .max()
                     )
+                else:
+                    n_pars[col] = 1 - int(
+                        self._petab_problem.measurement_df[col].isna().all()
+                    )
 
         for _, simulation_condition in simulation_conditions.iterrows():
             query = " & ".join(