Fix nitpicks (formatting and typing)

da/api/common.py

@@ -1,41 +1,50 @@
 from abc import ABC, abstractmethod
 from dataclasses import dataclass
-from typing import Optional, List
+from typing import Optional, List, Sequence
 
+from da.common import Certificate
 from da.verifier import DABlob
 
+
 @dataclass
 class Metadata:
+    # index of VID certificate blob
     index: int
-    app_id: int 
+    # app identifier
+    app_id: bytes
+
 
 class BlobStore(ABC):
     @abstractmethod
-    def add(certificate, metadata):
+    def add(self, certificate: Certificate, metadata: Metadata):
+        """
+        Raises: ValueError if there is already a registered certificate fot the given metadata
+        """
         pass
 
     @abstractmethod
-    def get_multiple(app_id, indexes) -> List[DABlob]:
+    def get_multiple(self, app_id: bytes, indexes: Sequence[int]) -> List[Optional[DABlob]]:
         pass
 
-class Api:
+
+class DAApi:
     def __init__(self, bs: BlobStore):
         self.store = bs
 
-    """
-    Write method should be used by a service that is able to retrieve verified certificates
-    from the latest Block. Once a certificate is retrieved, api creates a relation between
-    the blob of an original data, certificate and index for the app_id of the certificate.
-    """
-    def write(self, certificate, metadata):
+    def write(self, certificate: Certificate, metadata: Metadata):
+        """
+        Write method should be used by a service that is able to retrieve verified certificates
+        from the latest Block. Once a certificate is retrieved, api creates a relation between
+        the blob of an original data, certificate and index for the app_id of the certificate.
+        Raises: ValueError if there is already a registered certificate for a given metadata
+        """
         self.store.add(certificate, metadata)
-        return
 
-    """
-    Read method should accept only `app_id` and a list of indexes. The returned list of
-    blobs should be ordered in the same sequence as `indexes` in a request.
-    If node does not have the blob for some indexes, then it should add None object as an
-    item.
-    """
-    def read(self, app_id, indexes) -> Optional[List[Optional[DABlob]]]:
+    def read(self, app_id, indexes) -> List[Optional[DABlob]]:
+        """
+        Read method should accept only `app_id` and a list of indexes. The returned list of
+        blobs should be ordered in the same sequence as `indexes` in a request.
+        If node does not have the blob for some indexes, then it should add None object as an
+        item.
+        """
         return self.store.get_multiple(app_id, indexes)

da/api/test_flow.py

@@ -3,10 +3,12 @@ from collections import defaultdict
 
 from da.api.common import *
 
+
 @dataclass
 class MockCertificate:
     cert_id: int
 
+
 class MockStore(BlobStore):
     def __init__(self):
         self.blob_store = {}
@@ -41,7 +43,7 @@ class TestFlow(TestCase):
         mock_store = MockStore()
         mock_store.populate(expected_blob, cert_id)
 
-        api = Api(mock_store)
+        api = DAApi(mock_store)
 
         api.write(cert_id, mock_meta)
         blobs = api.read(app_id, [idx])
@@ -58,7 +60,7 @@ class TestFlow(TestCase):
         mock_store = MockStore()
         mock_store.populate(expected_blob, cert_id)
 
-        api = Api(mock_store)
+        api = DAApi(mock_store)
 
         api.write(cert_id, mock_meta)
         with self.assertRaises(ValueError):