add exception if user inputs single mpid to get cohesive energy function

Author: esoteric-ephemera

mp_api/client/mprester.py

@@ -1359,6 +1359,13 @@ def get_cohesive_energy(
             (dict[str,float]) : The cohesive energies (in eV/atom or eV/formula unit) for
             each material, indexed by MPID.
         """
+        # Prevent user error
+        if isinstance(material_ids, str | MPID):
+            raise MPRestError(
+                "Input material IDs (even a single ID) as a list: "
+                f"`[{material_ids}]`"
+            )
+
         entry_preference = {
             k: i for i, k in enumerate(["GGA", "GGA_U", "SCAN", "R2SCAN"])
         }

tests/client/test_mprester.py

@@ -512,6 +512,10 @@ def test_get_cohesive_energy(self):
             v == pytest.approx(e_coh["noserial"][k]) for k, v in e_coh["serial"].items()
         )
 
+        with pytest.raises(MPRestError, match="Input material IDs"):
+            with MPRester() as mpr:
+                mpr.get_cohesive_energy("mp-1")
+
     @pytest.mark.parametrize(
         "chemsys, thermo_type",
         [