[backend][assetmodel] Implement has_code setter in AssetType

This will allow handling between asset types with and without
code associated.

beat/editor/backend/assetmodel.py

@@ -34,6 +34,7 @@ from PyQt5.QtCore import pyqtSlot
 from PyQt5.QtCore import pyqtProperty
 from PyQt5.QtCore import QStringListModel
 
+from beat.backend.python import utils
 from beat.core.schema import validate
 from beat.cmdline import common
 
@@ -170,6 +171,14 @@ class AssetType(Enum):
         asset_folder = os.path.join(prefix, self.path)
         return os.path.join(asset_folder, "{}.json".format(name))
 
+    def has_code(self):
+        """Returns whether this asset type contains code"""
+
+        if self.klass is None:
+            return False
+
+        return issubclass(self.storage, utils.CodeStorage)
+
 
 class AssetModel(QStringListModel):
     """The asset model present a list of available asset from a given type"""