Reorganize to limit lines per function, per pylint.

src/hats_import/catalog/run_import.py

@@ -19,18 +19,27 @@
 from hats_import.catalog.resume_plan import ResumePlan
 
 
-def run(args, client):
-    """Run catalog creation pipeline."""
+def _validate_arguments(args):
+    """
+    Verify that the args for run are valid: they exist, are of the appropriate type,
+    and do not specify an output which is a valid catalog.
+
+    Raises ValueError if they are invalid.
+    """
     if not args:
         raise ValueError("args is required and should be type ImportArguments")
     if not isinstance(args, ImportArguments):
         raise ValueError("args must be type ImportArguments")
 
-    # Verify that the planned output path is not occupied by a valid catalog
     potential_path = Path(args.output_path) / args.output_artifact_name
     if is_valid_catalog(potential_path):
         raise ValueError(f"Output path {potential_path} already contains a valid catalog")
 
+
+def run(args, client):
+    """Run catalog creation pipeline."""
+    _validate_arguments(args)
+
     resume_plan = ResumePlan(import_args=args)
 
     pickled_reader_file = os.path.join(resume_plan.tmp_path, "reader.pickle")