Address Lukas comments

Signed-off-by: Martin Vrachev <[email protected]>

Author: MVrachev

tuf/api/metadata.py

@@ -300,8 +300,7 @@ def from_dict(cls, signed_dict: JsonDict) -> 'Signed':
                 signed_dict['expires'])
         # NOTE: Any 'from_dict'(-like) conversions of fields that correspond
         # to a subclass should be performed in the 'from_dict' method of that
-        # subclass and also be written back into 'signed_dict' before calling
-        # super().from_dict.
+        # subclass and assigned to the below returned object.
 
         # NOTE: cls might be a subclass of Signed, if 'from_dict' was called on
         # that subclass (see e.g. Metadata.from_dict).
@@ -380,6 +379,10 @@ def __init__(
             self, _type: str=None, version: int=None, spec_version: str=None,
             expires: datetime=None, consistent_snapshot: bool=None,
             keys: JsonDict=None, roles: JsonDict=None) -> None:
+
+        # TODO: Add sensible defaults when we have input validation.
+        # See issue https://github.com/theupdateframework/tuf/issues/1140
+        # We need default values to create empty objects in Signed.from_dict()
         super().__init__(_type, version, spec_version, expires)
         # TODO: Add classes for keys and roles
         self.consistent_snapshot = consistent_snapshot
@@ -492,6 +495,10 @@ def __init__(
             self, _type: str=None, version: int=None, spec_version: str=None,
             expires: datetime=None, meta: Dict[str, MetadataInfo]=None
             ) -> None:
+
+        # TODO: Add sensible defaults when we have input validation.
+        # See issue https://github.com/theupdateframework/tuf/issues/1140
+        # We need default values to create empty objects in Signed.from_dict()
         super().__init__(_type, version, spec_version, expires)
         self.meta = meta
 
@@ -536,7 +543,7 @@ class Snapshot(Signed):
         meta: A dictionary that contains information about targets metadata::
 
             {
-                'targets.json': <MetadataInfo INSTANCE>
+                'targets.json': <MetadataInfo INSTANCE>,
                 '<DELEGATED TARGETS ROLE 1>.json': <MetadataInfo INSTANCE>,
                 '<DELEGATED TARGETS ROLE 2>.json': <MetadataInfo INSTANCE>,
                 ...
@@ -547,6 +554,10 @@ def __init__(
             self, _type: str=None, version: int=None, spec_version: str=None,
             expires: datetime=None, meta: Dict[str, MetadataInfo]=None
             ) -> None:
+
+        # TODO: Add sensible defaults when we have input validation.
+        # See issue https://github.com/theupdateframework/tuf/issues/1140
+        # We need default values to create empty objects in Signed.from_dict()
         super().__init__(_type, version, spec_version, expires)
         self.meta = meta
 
@@ -694,6 +705,9 @@ def __init__(
             self, _type: str=None, version: int=None, spec_version: str=None,
             expires: datetime=None, targets: Dict[str, TargetInfo]=None,
             delegations: JsonDict=None) -> None:
+        # TODO: Add sensible defaults when we have input validation.
+        # See issue https://github.com/theupdateframework/tuf/issues/1140
+        # We need default values to create empty objects in Signed.from_dict()
         super().__init__(_type, version, spec_version, expires)
         self.targets = targets