diff --git a/pandas/io/formats/css.py b/pandas/io/formats/css.py
index 334daab3083c0..f74be62fe818e 100644
--- a/pandas/io/formats/css.py
+++ b/pandas/io/formats/css.py
@@ -15,25 +15,13 @@ class CSSWarning(UserWarning):
 
 
 def _side_expander(prop_fmt: str):
-    """
-    Parameters
-    ----------
-    prop_fmt : str
-    """
-
     def expand(self, prop, value: str):
-        """
-        Parameters
-        ----------
-        prop
-        value : str
-        """
         tokens = value.split()
         try:
             mapping = self.SIDE_SHORTHANDS[len(tokens)]
         except KeyError:
             warnings.warn(
-                f"Could not expand {prop}: {value}", CSSWarning,
+                f'Could not expand "{prop}: {value}"', CSSWarning,
             )
             return
         for key, idx in zip(self.SIDES, mapping):
diff --git a/pandas/io/formats/csvs.py b/pandas/io/formats/csvs.py
index 9c6fb46d04db0..153de2b60d093 100644
--- a/pandas/io/formats/csvs.py
+++ b/pandas/io/formats/csvs.py
@@ -5,13 +5,14 @@
 import csv as csvlib
 from io import StringIO
 import os
-from typing import List, Optional, Sequence, Union
+from typing import Hashable, List, Optional, Sequence, Union
 import warnings
 from zipfile import ZipFile
 
 import numpy as np
 
 from pandas._libs import writers as libwriters
+from pandas._typing import FilePathOrBuffer
 
 from pandas.core.dtypes.generic import (
     ABCDatetimeIndex,
@@ -21,8 +22,6 @@
 )
 from pandas.core.dtypes.missing import notna
 
-from pandas._typing import FilePathOrBuffer
-
 from pandas.io.common import (
     get_compression_method,
     get_filepath_or_buffer,
@@ -38,11 +37,11 @@ def __init__(
         path_or_buf: Optional[FilePathOrBuffer[str]] = None,
         sep: str = ",",
         na_rep: str = "",
-        float_format=None,
+        float_format: Optional[str] = None,
         cols=None,
-        header: Union[bool, Sequence[str]] = True,
+        header: Union[bool, Sequence[Hashable]] = True,
         index: bool = True,
-        index_label=None,
+        index_label: Optional[Union[bool, Hashable, Sequence[Hashable]]] = None,
         mode: str = "w",
         encoding: Optional[str] = None,
         compression="infer",
@@ -52,7 +51,7 @@ def __init__(
         quotechar: Optional[str] = '"',
         date_format: Optional[str] = None,
         doublequote: bool = True,
-        escapechar=None,
+        escapechar: Optional[str] = None,
         decimal: Optional[str] = ".",
     ):
         self.obj = obj