diff --git a/cassis/json.py b/cassis/json.py
index b3ce2d2..6c39384 100644
--- a/cassis/json.py
+++ b/cassis/json.py
@@ -8,12 +8,35 @@
 from toposort import toposort_flatten
 
 from cassis.cas import NAME_DEFAULT_SOFA, Cas, IdGenerator, Sofa, View
-from cassis.typesystem import TYPE_NAME_ANNOTATION, TypeSystem, is_predefined, merge_typesystems, TYPE_NAME_SOFA, \
-    FEATURE_BASE_NAME_SOFAARRAY, array_type_name_for_type, FEATURE_BASE_NAME_SOFASTRING, FEATURE_BASE_NAME_SOFAID, \
-    FEATURE_BASE_NAME_SOFAMIME, FEATURE_BASE_NAME_SOFANUM, FEATURE_BASE_NAME_SOFAURI, TYPE_NAME_FS_ARRAY, \
-    TYPE_NAME_BYTE_ARRAY, TYPE_NAME_FLOAT_ARRAY, TYPE_NAME_DOUBLE_ARRAY, TypeSystemMode, TYPE_NAME_DOCUMENT_ANNOTATION, \
-    Type, Feature, TYPE_NAME_TOP, is_primitive_array, TYPE_NAME_FLOAT, TYPE_NAME_DOUBLE, \
-    element_type_name_for_array_type, is_primitive, is_array
+from cassis.typesystem import (
+    TYPE_NAME_ANNOTATION,
+    TypeSystem,
+    is_predefined,
+    merge_typesystems,
+    TYPE_NAME_SOFA,
+    FEATURE_BASE_NAME_SOFAARRAY,
+    array_type_name_for_type,
+    FEATURE_BASE_NAME_SOFASTRING,
+    FEATURE_BASE_NAME_SOFAID,
+    FEATURE_BASE_NAME_SOFAMIME,
+    FEATURE_BASE_NAME_SOFANUM,
+    FEATURE_BASE_NAME_SOFAURI,
+    TYPE_NAME_FS_ARRAY,
+    TYPE_NAME_BYTE_ARRAY,
+    TYPE_NAME_FLOAT_ARRAY,
+    TYPE_NAME_DOUBLE_ARRAY,
+    TypeSystemMode,
+    TYPE_NAME_DOCUMENT_ANNOTATION,
+    Type,
+    Feature,
+    TYPE_NAME_TOP,
+    is_primitive_array,
+    TYPE_NAME_FLOAT,
+    TYPE_NAME_DOUBLE,
+    element_type_name_for_array_type,
+    is_primitive,
+    is_array,
+)
 
 RESERVED_FIELD_PREFIX = "%"
 REF_FEATURE_PREFIX = "@"