prompt: You will be provided with a partial code base and an issue statement explaining a problem to resolve.
  <issue>
  [DataFrame] Error checking on Pandas version
  We need better reporting for issues with the Pandas version on a user's system. 
  
  </issue>
  <code>
  [start of python/ray/dataframe/__init__.py]
  1 from __future__ import absolute_import
  2 from __future__ import division
  3 from __future__ import print_function
  4 import threading
  5 
  6 DEFAULT_NPARTITIONS = 4
  7 
  8 
  9 def set_npartition_default(n):
  10     global DEFAULT_NPARTITIONS
  11     DEFAULT_NPARTITIONS = n
  12 
  13 
  14 def get_npartitions():
  15     return DEFAULT_NPARTITIONS
  16 
  17 
  18 # We import these file after above two function
  19 # because they depend on npartitions.
  20 from .dataframe import DataFrame  # noqa: 402
  21 from .dataframe import from_pandas  # noqa: 402
  22 from .dataframe import to_pandas  # noqa: 402
  23 from .series import Series  # noqa: 402
  24 from .io import (read_csv, read_parquet)  # noqa: 402
  25 
  26 __all__ = [
  27     "DataFrame", "from_pandas", "to_pandas", "Series", "read_csv",
  28     "read_parquet"
  29 ]
  30 
  31 try:
  32     if threading.current_thread().name == "MainThread":
  33         import ray
  34         ray.init()
  35 except AssertionError:
  36     pass
  37
  [end of python/ray/dataframe/__init__.py]
  </code>
  
  I need you to solve this issue by generating a single patch file that I can apply directly to this repository using git apply. Please respond with a single patch file in the following format.
  <patch>
  diff --git a/file.py b/file.py
  --- a/file.py
  +++ b/file.py
  @@ -1,27 +1,35 @@
   def euclidean(a, b):
  -    while b:
  -        a, b = b, a % b
  -    return a
  +    if b == 0:
  +        return a
  +    return euclidean(b, a % b)
   
   
   def bresenham(x0, y0, x1, y1):
       points = []
       dx = abs(x1 - x0)
       dy = abs(y1 - y0)
  -    sx = 1 if x0 < x1 else -1
  -    sy = 1 if y0 < y1 else -1
  -    err = dx - dy
  +    x, y = x0, y0
  +    sx = -1 if x0 > x1 else 1
  +    sy = -1 if y0 > y1 else 1
   
  -    while True:
  -        points.append((x0, y0))
  -        if x0 == x1 and y0 == y1:
  -            break
  -        e2 = 2 * err
  -        if e2 > -dy:
  -            err -= dy
  -            x0 += sx
  -        if e2 < dx:
  -            err += dx
  -            y0 += sy
  +    if dx > dy:
  +        err = dx / 2.0
  +        while x != x1:
  +            points.append((x, y))
  +            err -= dy
  +            if err < 0:
  +                y += sy
  +                err += dx
  +            x += sx
  +    else:
  +        err = dy / 2.0
  +        while y != y1:
  +            points.append((x, y))
  +            err -= dx
  +            if err < 0:
  +                x += sx
  +                err += dy
  +            y += sy
  +
  +    points.append((x, y))
       return points
  
  </patch>
golden_diff: diff --git a/python/ray/dataframe/__init__.py b/python/ray/dataframe/__init__.py
  --- a/python/ray/dataframe/__init__.py
  +++ b/python/ray/dataframe/__init__.py
  @@ -1,8 +1,18 @@
   from __future__ import absolute_import
   from __future__ import division
   from __future__ import print_function
  +
  +import pandas as pd
   import threading
   
  +pd_version = pd.__version__
  +pd_major = int(pd_version.split(".")[0])
  +pd_minor = int(pd_version.split(".")[1])
  +
  +if pd_major == 0 and pd_minor < 22:
  +    raise Exception("In order to use Pandas on Ray, please upgrade your Pandas"
  +                    " version to >= 0.22.")
  +
   DEFAULT_NPARTITIONS = 4
  
verification_info: {"golden_diff": "diff --git a/python/ray/dataframe/__init__.py b/python/ray/dataframe/__init__.py\n--- a/python/ray/dataframe/__init__.py\n+++ b/python/ray/dataframe/__init__.py\n@@ -1,8 +1,18 @@\n from __future__ import absolute_import\n from __future__ import division\n from __future__ import print_function\n+\n+import pandas as pd\n import threading\n \n+pd_version = pd.__version__\n+pd_major = int(pd_version.split(\".\")[0])\n+pd_minor = int(pd_version.split(\".\")[1])\n+\n+if pd_major == 0 and pd_minor < 22:\n+    raise Exception(\"In order to use Pandas on Ray, please upgrade your Pandas\"\n+                    \" version to >= 0.22.\")\n+\n DEFAULT_NPARTITIONS = 4\n", "issue": "[DataFrame] Error checking on Pandas version\nWe need better reporting for issues with the Pandas version on a user's system. \n", "before_files": [{"content": "from __future__ import absolute_import\nfrom __future__ import division\nfrom __future__ import print_function\nimport threading\n\nDEFAULT_NPARTITIONS = 4\n\n\ndef set_npartition_default(n):\n    global DEFAULT_NPARTITIONS\n    DEFAULT_NPARTITIONS = n\n\n\ndef get_npartitions():\n    return DEFAULT_NPARTITIONS\n\n\n# We import these file after above two function\n# because they depend on npartitions.\nfrom .dataframe import DataFrame  # noqa: 402\nfrom .dataframe import from_pandas  # noqa: 402\nfrom .dataframe import to_pandas  # noqa: 402\nfrom .series import Series  # noqa: 402\nfrom .io import (read_csv, read_parquet)  # noqa: 402\n\n__all__ = [\n    \"DataFrame\", \"from_pandas\", \"to_pandas\", \"Series\", \"read_csv\",\n    \"read_parquet\"\n]\n\ntry:\n    if threading.current_thread().name == \"MainThread\":\n        import ray\n        ray.init()\nexcept AssertionError:\n    pass\n", "path": "python/ray/dataframe/__init__.py"}]}