ENH: Add dunder accessors to Pydantic RootModels

src/fmu/dataio/_model/fields.py

@@ -134,6 +134,14 @@ class Parameters(RootModel):
     root: Dict[str, Union[Parameters, int, float, str]]
     """A dictionary representing parameters as-is from parameters.txt."""
 
+    def __iter__(self) -> Any:
+        # Using ´Any´ as return type here as mypy is having issues
+        # resolving the correct type
+        return iter(self.root)
+
+    def __getitem__(self, item: str) -> Union[Parameters, int, float, str]:
+        return self.root[item]
+
 
 class Aggregation(BaseModel):
     """

src/fmu/dataio/_model/global_configuration.py

@@ -108,6 +108,14 @@ class Stratigraphy(RootModel[Dict[str, StratigraphyElement]]):
     A collection of StratigraphyElement instances, accessible by keys.
     """
 
+    def __iter__(self) -> Any:
+        # Using ´Any´ as return type here as mypy is having issues
+        # resolving the correct type
+        return iter(self.root)
+
+    def __getitem__(self, item: str) -> StratigraphyElement:
+        return self.root[item]
+
 
 class GlobalConfiguration(BaseModel):
     """

tests/test_units/test_dunder_methods.py

@@ -0,0 +1,94 @@
+"""Explicitly test all dunder methods."""
+
+import pytest
+
+from fmu.dataio._model.fields import Parameters
+from fmu.dataio._model.global_configuration import Stratigraphy, StratigraphyElement
+
+# --------------------------------------------------------------------------------------
+# Stratigraphy
+# --------------------------------------------------------------------------------------
+
+
+@pytest.fixture(name="testdata_stratigraphy", scope="function")
+def _fixture_testdata_stratigraphy() -> Stratigraphy:
+    """
+    Return a dict of StratigraphyElement instances.
+    """
+    return Stratigraphy(
+        root={
+            "TopStratUnit1": StratigraphyElement(
+                name="Stratigraphic Unit 1",
+                stratigraphic=True,
+                alias=["TopSU1", "TopLayer1"],
+            ),
+            "TopStratUnit2": StratigraphyElement(
+                name="Stratigraphic Unit 2",
+                stratigraphic=True,
+                alias=["TopSU2", "TopLayer2"],
+            ),
+            "TopStratUnit3": StratigraphyElement(
+                name="Stratigraphic Unit 3",
+                stratigraphic=True,
+                alias=["TopSU3", "TopLayer3"],
+            ),
+        }
+    )
+
+
+def test_stratigraphy_dunder_iter(testdata_stratigraphy):
+    try:
+        count = 0
+        for item in testdata_stratigraphy:
+            count += 1
+        assert count == 3
+    except Exception:
+        assert False, "Stratigraphy class does not have __iter__()"
+
+
+def test_stratigraphy_dunder_getitem(testdata_stratigraphy):
+    try:
+        testdata_stratigraphy["TopStratUnit2"]
+    except Exception:
+        assert False, "Stratigraphy class does not have __getitem__()"
+
+
+# --------------------------------------------------------------------------------------
+# Parameters
+# --------------------------------------------------------------------------------------
+
+
+@pytest.fixture(name="testdata_parameters", scope="function")
+def _fixture_testdata_parameters() -> Parameters:
+    """
+    Return a nested dict of Parameter instances.
+    """
+    return Parameters(
+        root={
+            "p1": 42,
+            "p2": "not so nested",
+            "p3": Parameters(
+                root={
+                    "p3_1": 42.3,
+                    "p3_2": "more nested",
+                }
+            ),
+        }
+    )
+
+
+def test_parameters_dunder_iter(testdata_parameters):
+    try:
+        count = 0
+        for item in testdata_parameters:
+            count += 1
+        assert count == 3
+    except Exception:
+        assert False, "Parameters class does not have __iter__()"
+
+
+def test_parameters_dunder_getitem(testdata_parameters):
+    try:
+        testdata_parameters["p2"]
+    except Exception:
+        assert False, "Parameters class does not have __getitem__()"