From 6b55150e80958f1de4719088726541b7256fe7ef Mon Sep 17 00:00:00 2001
From: Jiaming Yuan <jm.yuan@outlook.com>
Date: Thu, 2 Jun 2022 18:04:46 +0800
Subject: [PATCH] Fix pylint errors. (#7967)

---
 python-package/setup.py            |  2 +-
 python-package/xgboost/callback.py |  2 +-
 python-package/xgboost/core.py     | 15 ++++++++-------
 python-package/xgboost/dask.py     |  2 +-
 4 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/python-package/setup.py b/python-package/setup.py
index 6c83feca0..b4f05e027 100644
--- a/python-package/setup.py
+++ b/python-package/setup.py
@@ -96,7 +96,7 @@ class BuildExt(build_ext.build_ext):  # pylint: disable=too-many-ancestors
 
     logger = logging.getLogger('XGBoost build_ext')
 
-    # pylint: disable=too-many-arguments,no-self-use
+    # pylint: disable=too-many-arguments
     def build(
         self,
         src_dir: str,
diff --git a/python-package/xgboost/callback.py b/python-package/xgboost/callback.py
index 021ccd972..102d53ce4 100644
--- a/python-package/xgboost/callback.py
+++ b/python-package/xgboost/callback.py
@@ -1,5 +1,5 @@
 # coding: utf-8
-# pylint: disable=invalid-name, too-many-statements, no-self-use
+# pylint: disable=invalid-name, too-many-statements
 # pylint: disable=too-many-arguments
 """Callback library containing training routines.  See :doc:`Callback Functions
 </python/callbacks>` for a quick introduction.
diff --git a/python-package/xgboost/core.py b/python-package/xgboost/core.py
index 6ec1fbf45..acab3ee52 100644
--- a/python-package/xgboost/core.py
+++ b/python-package/xgboost/core.py
@@ -3,6 +3,7 @@
 """Core XGBoost Library."""
 from abc import ABC, abstractmethod
 from collections.abc import Mapping
+import copy
 from typing import List, Optional, Any, Union, Dict, TypeVar
 from typing import Callable, Tuple, cast, Sequence, Type, Iterable
 import ctypes
@@ -1638,7 +1639,7 @@ class Booster:
         booster: `Booster`
             a copied booster model
         """
-        return self.__copy__()
+        return copy.copy(self)
 
     def attr(self, key: str) -> Optional[str]:
         """Get attribute string from the Booster.
@@ -2370,15 +2371,15 @@ class Booster:
         ret = self.get_dump(fmap, with_stats, dump_format)
         if dump_format == 'json':
             fout_obj.write('[\n')
-            for i, _ in enumerate(ret):
-                fout_obj.write(ret[i])
+            for i, val in enumerate(ret):
+                fout_obj.write(val)
                 if i < len(ret) - 1:
                     fout_obj.write(",\n")
             fout_obj.write('\n]')
         else:
-            for i, _ in enumerate(ret):
+            for i, val in enumerate(ret):
                 fout_obj.write(f"booster[{i}]:\n")
-                fout_obj.write(ret[i])
+                fout_obj.write(val)
         if need_close:
             fout_obj.close()
 
@@ -2667,8 +2668,8 @@ class Booster:
         values = []
         # pylint: disable=consider-using-f-string
         regexp = re.compile(r"\[{0}<([\d.Ee+-]+)\]".format(feature))
-        for i, _ in enumerate(xgdump):
-            m = re.findall(regexp, xgdump[i])
+        for i, val in enumerate(xgdump):
+            m = re.findall(regexp, val)
             values.extend([float(x) for x in m])
 
         n_unique = len(np.unique(values))
diff --git a/python-package/xgboost/dask.py b/python-package/xgboost/dask.py
index 4363feac7..f9176c023 100644
--- a/python-package/xgboost/dask.py
+++ b/python-package/xgboost/dask.py
@@ -1719,7 +1719,7 @@ class DaskScikitLearnBase(XGBModel):
     """Implementation of the Scikit-Learn API for XGBoost.""", ["estimators", "model"]
 )
 class DaskXGBRegressor(DaskScikitLearnBase, XGBRegressorBase):
-    # pylint: disable=missing-class-docstring
+    """dummy doc string to workaround pylint, replaced by the decorator."""
     async def _fit_async(
         self,
         X: _DaskCollection,