fix tests and update changelog

Author: valentinsulzer

CHANGELOG.md

@@ -9,6 +9,7 @@
 
 ## Bug fixes
 
+- Parameter sets can now contain the key "chemistry", and will ignore its value (this previously would give errors in some cases) ([#2901](https://github.com/pybamm-team/PyBaMM/pull/2901))
 - Fixed a bug in the discretisation of initial conditions of a scaled variable ([#2856](https://github.com/pybamm-team/PyBaMM/pull/2856))
 - Fixed keyerror on "all" when getting sensitivities from IDAKLU solver([#2883](https://github.com/pybamm-team/PyBaMM/pull/2883))
 

pybamm/parameters/parameter_values.py

@@ -71,13 +71,13 @@ def __init__(self, values, chemistry=None):
                 self.update_from_chemistry(values)
             else:
                 # Remove chemistry if present
-                values.pop("chemistry")
+                values.pop("chemistry", None)
                 self.update(values, check_already_exists=False)
         else:
             # Check if values is a named parameter set
             if isinstance(values, str) and values in pybamm.parameter_sets:
                 values = pybamm.parameter_sets[values]
-                values.pop("chemistry")
+                values.pop("chemistry", None)
                 self.update(values, check_already_exists=False)
 
             else:

tests/unit/test_parameters/test_parameter_values.py

@@ -56,6 +56,10 @@ def test_init(self):
         self.assertIn("a", param.keys())
         self.assertIn(1, param.values())
 
+        # from dict "chemistry" key gets removed
+        param = pybamm.ParameterValues({"a": 1, "chemistry": "lithium-ion"})
+        self.assertNotIn("chemistry", param.keys())
+
         # from file
         param = pybamm.ParameterValues(
             "lithium_ion/testing_only/positive_electrodes/lico2_Ai2020/parameters.csv"