Push much looping and merging of infering type vars into ValueSet

jedi/inference/gradual/base.py

@@ -209,13 +209,12 @@ class GenericClass(ClassMixin, DefineGenericBase):
         if annotation_name == 'Iterable' and not is_class_value:
             given = self.get_generics()
             if given:
-                for nested_annotation_value in given[0]:
-                    merge_type_var_dicts(
-                        type_var_dict,
-                        nested_annotation_value.infer_type_vars(
-                            value_set.merge_types_of_iterate(),
-                        ),
-                    )
+                merge_type_var_dicts(
+                    type_var_dict,
+                    given[0].infer_type_vars(
+                        value_set.merge_types_of_iterate(),
+                    ),
+                )
         else:
             # Note: we need to handle the MRO _in order_, so we need to extract
             # the elements from the set first, then handle them, even if we put