Allow nullable types (optional list/set) to define one-to-many relations

pysqlsync/formation/py_to_sql.py

@@ -39,12 +39,14 @@
     is_generic_set,
     is_type_enum,
     is_type_literal,
+    is_type_optional,
     is_type_union,
     unwrap_annotated_type,
     unwrap_generic_list,
     unwrap_generic_set,
     unwrap_literal_types,
     unwrap_literal_values,
+    unwrap_optional_type,
     unwrap_union_types,
 )
 from strong_typing.topological import type_topological_sort
@@ -497,6 +499,9 @@ def _get_relationship(
         :returns: A tuple of host relationship type (e.g. list) and host field type.
         """
 
+        if is_type_optional(field_type):
+            return self._get_relationship(unwrap_optional_type(field_type))
+
         field_type = unwrap_annotated_type(field_type)
 
         # relations must be one-to-many