rebased "Introduction of ItemSource interface" patch

cellxgene_gateway/items/file/fileitem.py

@@ -0,0 +1,27 @@
+# Copyright 2019 Novartis Institutes for BioMedical Research Inc. Licensed
+# under the Apache License, Version 2.0 (the "License"); you may not use
+# this file except in compliance with the License. You may obtain a copy
+# of the License at http://www.apache.org/licenses/LICENSE-2.0. Unless
+# required by applicable law or agreed to in writing, software distributed
+# under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES
+# OR CONDITIONS OF ANY KIND, either express or implied. See the License for
+# the specific language governing permissions and limitations under the License.
+
+import os
+
+from cellxgene_gateway.items.item import Item
+
+
+class FileItem(Item):
+    """e.g. FileItem(subpath = subpath, name = filename, type = ItemType.h5ad)
+
+    The Item superclass expects a 'name' and 'type'.
+    """
+
+    def __init__(self, subpath: str, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.subpath = subpath
+
+    @property
+    def descriptor(self) -> str:
+        return os.path.join(self.subpath, self.name).strip("/")