New API: Disable irrelevant pylint warnings

Warnings E1120 and W0212 are irrelevant in one specific case, but
rule E1101 creates a lot of false-positives in tuf/metadata/api.

For example, there are 4 false-positives in this file related
to "meta" and "targets" fields not existing in "signed_dict" in
"from_dict" functions in Timestamp, Snapshot and Targets classes.

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

Author: MVrachev

tuf/api/metadata.py

@@ -1,3 +1,5 @@
+# pylint: disable=E1101
+
 """TUF role metadata model.
 
 This module provides container classes for TUF role metadata, including methods
@@ -291,8 +293,11 @@ def from_dict(cls, signed_dict: JsonDict) -> 'Signed':
 
         # Create empty object with default or parametrized constructor with
         # default arguments.
-        obj = cls()
-        obj._type = signed_dict['_type']
+        # Warnings about rules E1120 (no-value-for-parameter) and W0212
+        # (protected-access) are not relevant here because cls is most likely
+        # a descendant of "Signed" and we need to setup the appropriate fields.
+        obj = cls() # pylint: disable=E1120
+        obj._type = signed_dict['_type'] # pylint: disable=W0212
         obj.version = signed_dict['version']
         obj.spec_version = signed_dict['spec_version']
         # Convert 'expires' TUF metadata string to a datetime object, which is