split helpers into smaller files

mypy_django_plugin/lib/metadata.py

@@ -0,0 +1,23 @@
+from typing import Any, Dict, List
+
+from mypy.nodes import TypeInfo
+
+
+def get_django_metadata(model_info: TypeInfo) -> Dict[str, Any]:
+    return model_info.metadata.setdefault('django', {})
+
+
+def get_related_field_primary_key_names(base_model: TypeInfo) -> List[str]:
+    return get_django_metadata(base_model).setdefault('related_field_primary_keys', [])
+
+
+def get_fields_metadata(model: TypeInfo) -> Dict[str, Any]:
+    return get_django_metadata(model).setdefault('fields', {})
+
+
+def get_lookups_metadata(model: TypeInfo) -> Dict[str, Any]:
+    return get_django_metadata(model).setdefault('lookups', {})
+
+
+def get_related_managers_metadata(model: TypeInfo) -> Dict[str, Any]:
+    return get_django_metadata(model).setdefault('related_managers', {})