switched to using field.mandatory instead of comparing with NO_DEFAULT

Author: tclose

generate.py

@@ -397,7 +397,7 @@ def get_value(type_):
                 raise NotImplementedError
             return value
 
-        if field.default is not NO_DEFAULT:
+        if not field.mandatory:
             value = field.default
         elif field.allowed_values:
             value = repr(field.allowed_values[0])