Use comprehension instead of builder pattern

Author: uranusjr

src/pip/_internal/commands/show.py

@@ -100,12 +100,11 @@ def _get_requiring_packages(current_dist: BaseDistribution) -> Iterator[str]:
         except KeyError:
             continue
 
-        requires = set()
-        # Avoid duplicates in requirements due to environment markers
-        for req in dist.iter_dependencies():
-            if req.name not in requires:
-                requires.add(req.name)
-        requires = sorted(requires, key=str.lower)
+        requires = sorted(
+            # Avoid duplicates in requirements (e.g. due to environment markers).
+            {req.name for req in dist.iter_dependencies()},
+            key=str.lower,
+        )
         required_by = sorted(_get_requiring_packages(dist), key=str.lower)
 
         try: