PERF: lazify type-check import (#28342)

Author: jbrockmendel

pandas/io/formats/format.py

@@ -5,6 +5,7 @@
 
 import codecs
 from contextlib import contextmanager
+from datetime import tzinfo
 import decimal
 from functools import partial
 from io import StringIO
@@ -27,8 +28,6 @@
 )
 from unicodedata import east_asian_width
 
-from dateutil.tz.tz import tzutc
-from dateutil.zoneinfo import tzfile
 import numpy as np
 
 from pandas._config.config import get_option, set_option
@@ -1552,9 +1551,7 @@ def _is_dates_only(
 
 
 def _format_datetime64(
-    x: Union[NaTType, Timestamp],
-    tz: Optional[Union[tzfile, tzutc]] = None,
-    nat_rep: str = "NaT",
+    x: Union[NaTType, Timestamp], tz: Optional[tzinfo] = None, nat_rep: str = "NaT"
 ) -> str:
     if x is None or (is_scalar(x) and isna(x)):
         return nat_rep