Improve documentation/text

Signed-off-by: Hritik Vijay <hritikxx8@gmail.com>

Author: Hritik14

vulnerabilities/improver.py

@@ -1,6 +1,7 @@
 import dataclasses
 import logging
 from typing import List
+from typing import Iterable
 from typing import Optional
 from uuid import uuid4
 
@@ -72,8 +73,11 @@ def from_advisory_data(cls, advisory_data, confidence, affected_purls, fixed_pur
 
 class Improver:
     """
-    Improvers are responsible to improve the already imported data by a datasource.
-    Inferences regarding the data could be generated based on multiple factors.
+    Improvers are responsible to improve already imported data by an importer.
+    An improver is required to override the ``interesting_advisories`` property method to return a
+    QuerySet of ``Advisory`` objects. These advisories are then passed to ``get_inferences`` method
+    which is responsible for returning an iterable of ``Inferences`` for that particular
+    ``Advisory``
     """
 
     @property
@@ -83,7 +87,7 @@ def interesting_advisories(self) -> QuerySet:
         """
         raise NotImplementedError
 
-    def get_inferences(self, advisory_data: AdvisoryData) -> List[Inference]:
+    def get_inferences(self, advisory_data: AdvisoryData) -> Iterable[Inference]:
         """
         Generate and return Inferences for the given advisory data
         """

vulnerabilities/management/commands/improve.py

@@ -56,7 +56,7 @@ def handle(self, *args, **options):
 
         sources = options["sources"]
         if not sources:
-            raise CommandError('Please provide at least one improver to run use "--all".')
+            raise CommandError('Please provide at least one improver to run or use "--all".')
 
         self.improve_data(validate_improvers(sources))