Improve typing

Author: jacob720

src/daq_config_server/converters/models.py

@@ -64,5 +64,5 @@ def get_value(
 
         return target_row[target_column_index]
 
-    def columns(self):
+    def columns(self) -> list[list[int | float]]:
         return [[row[i] for row in self.rows] for i in range(len(self.column_names))]