Fix DeprecationWarning: invalid escape sequence \d (#950)

* Fix DeprecationWarning: invalid escape sequence \d

* Resolves #949
* Removes the duplicated line and fixes in one place

* Lint

* Fix circular import

Author: devin-petersohn

modin/engines/ray/generic/io.py

@@ -1,7 +1,6 @@
 import pandas
 
 import os
-import re
 import numpy as np
 import math
 import warnings
@@ -14,8 +13,6 @@
 if __execution_engine__ == "Ray":
     import ray
 
-PQ_INDEX_REGEX = re.compile("__index_level_\d+__")  # noqa W605
-
 
 class RayIO(BaseIO):
 
@@ -88,6 +85,7 @@ def read_parquet(cls, path, engine, columns, **kwargs):
         """
 
         from pyarrow.parquet import ParquetFile, ParquetDataset
+        from modin.pandas.io import PQ_INDEX_REGEX
 
         if cls.read_parquet_remote_task is None:
             return super(RayIO, cls).read_parquet(path, engine, columns, **kwargs)

modin/pandas/io.py

@@ -9,7 +9,7 @@
 from .dataframe import DataFrame
 from modin.data_management.factories import BaseFactory
 
-PQ_INDEX_REGEX = re.compile("__index_level_\d+__")  # noqa W605
+PQ_INDEX_REGEX = re.compile(r"__index_level_\d+__")
 
 
 # Parquet