is_relevant_table_row should raise a custom exception for unknown items, find_relevant_table_rows should handle the rest

src/mwfin/exceptions.py

@@ -0,0 +1,10 @@
+class WrongAssumptions(Exception):
+    pass
+
+
+class UnexpectedMarkup(WrongAssumptions):
+    pass
+
+
+class UnknownFinancialStatementItem(WrongAssumptions):
+    pass