diff --git a/model.py b/model.py
index e6711c0..6fa45d5 100644
--- a/model.py
+++ b/model.py
@@ -248,7 +248,20 @@ class CaseBase:
         )
 
     def get_values_by_field(self, field: str) -> set[str]:
-        
+        """
+        get the distinct values by the fields
+
+        Args:
+            self: List with corresponding values
+            field: a string value that must be contained in self
+
+        Returns:
+            the distinct values
+
+        Raises:
+            ValueError: if the field value not in the 'problem' or 'solution' list
+        """
+
         if field not in list(self.fields["problem"]) + list(self.fields["solution"]):
             raise ValueError(f"unknown field {field}")