FIX: Make quarterly.csv development dates ISO 8601-compatible.

chainladder/core/tests/test_triangle.py

@@ -1061,3 +1061,23 @@ def test_xs(clrd):
     assert clrd.xs('comauto',level=1).index.equals(clrd.xs('comauto',level='LOB').index)
 
 
+def test_to_datetime_uninferrable_format_raises() -> None:
+    """
+    Initialize a triangle with incorrect date format on the origin axis. Should raise a ValueError.
+
+    Returns
+    -------
+    None
+
+    """
+    with pytest.raises(ValueError, match="Unable to infer datetime"):
+        cl.Triangle(
+            data={
+                'origin': ['1995/Q1', '1996/Q1'],
+                'development': ['1995Q1', '1996Q1'],
+                'value': [1.0, 2.0]},
+            origin='origin',
+            development='development',
+            columns='value',
+            cumulative=True
+        )

chainladder/core/triangle.py

@@ -34,7 +34,7 @@ class Triangle(TriangleBase):
 
     Parameters
     ----------
-    data: DataFrame or DataFrameXchg, or dict
+    data: DataFrame | DataFrameXchg | dict
         A single dataframe that contains columns representing all other
         arguments to the Triangle constructor. One may supply a DataFrame-like
         object (referred to as DataFrameXchg) supporting the __dataframe__