prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  Worker dies when passed pandas DataFrame.
  ### System information
  - **Ray version**: 0.3.0
  - **Python version**: 3.6.0
  - **Exact command to reproduce**:
  
  ```python
  import pandas as pd
  import ray
  
  pd.__version__  # '0.19.2'
  
  ray.init()
  
  df = pd.DataFrame(data={'col1': [1, 2, 3, 4], 'col2': [3, 4, 5, 6]})
  
  @ray.remote
  def f(x):
      pass
  
  f.remote(df)
  ```
  
  The last line causes the following error to be printed in the background.
  
  ```
  A worker died or was killed while executing a task.
  ```
  
  cc @devin-petersohn
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `python/ray/dataframe/__init__.py`
  Content:
  ```
  1 from __future__ import absolute_import
  2 from __future__ import division
  3 from __future__ import print_function
  4 
  5 from .dataframe import DataFrame
  6 from .dataframe import from_pandas
  7 from .dataframe import to_pandas
  8 from .series import Series
  9 import ray
  10 import pandas as pd
  11 
  12 __all__ = ["DataFrame", "from_pandas", "to_pandas", "Series"]
  13 
  14 ray.register_custom_serializer(pd.DataFrame, use_pickle=True)
  15 ray.register_custom_serializer(pd.core.indexes.base.Index, use_pickle=True)
  16
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
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
  @@ -6,10 +6,5 @@
   from .dataframe import from_pandas
   from .dataframe import to_pandas
   from .series import Series
  -import ray
  -import pandas as pd
   
   __all__ = ["DataFrame", "from_pandas", "to_pandas", "Series"]
  -
  -ray.register_custom_serializer(pd.DataFrame, use_pickle=True)
  -ray.register_custom_serializer(pd.core.indexes.base.Index, use_pickle=True)
  
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@@ -6,10 +6,5 @@\n from .dataframe import from_pandas\n from .dataframe import to_pandas\n from .series import Series\n-import ray\n-import pandas as pd\n \n __all__ = [\"DataFrame\", \"from_pandas\", \"to_pandas\", \"Series\"]\n-\n-ray.register_custom_serializer(pd.DataFrame, use_pickle=True)\n-ray.register_custom_serializer(pd.core.indexes.base.Index, use_pickle=True)\n", "issue": "Worker dies when passed pandas DataFrame.\n### System information\r\n- **Ray version**: 0.3.0\r\n- **Python version**: 3.6.0\r\n- **Exact command to reproduce**:\r\n\r\n```python\r\nimport pandas as pd\r\nimport ray\r\n\r\npd.__version__  # '0.19.2'\r\n\r\nray.init()\r\n\r\ndf = pd.DataFrame(data={'col1': [1, 2, 3, 4], 'col2': [3, 4, 5, 6]})\r\n\r\n@ray.remote\r\ndef f(x):\r\n    pass\r\n\r\nf.remote(df)\r\n```\r\n\r\nThe last line causes the following error to be printed in the background.\r\n\r\n```\r\nA worker died or was killed while executing a task.\r\n```\r\n\r\ncc @devin-petersohn\n", "before_files": [{"content": "from __future__ import absolute_import\nfrom __future__ import division\nfrom __future__ import print_function\n\nfrom .dataframe import DataFrame\nfrom .dataframe import from_pandas\nfrom .dataframe import to_pandas\nfrom .series import Series\nimport ray\nimport pandas as pd\n\n__all__ = [\"DataFrame\", \"from_pandas\", \"to_pandas\", \"Series\"]\n\nray.register_custom_serializer(pd.DataFrame, use_pickle=True)\nray.register_custom_serializer(pd.core.indexes.base.Index, use_pickle=True)\n", "path": "python/ray/dataframe/__init__.py"}], "after_files": [{"content": "from __future__ import absolute_import\nfrom __future__ import division\nfrom __future__ import print_function\n\nfrom .dataframe import DataFrame\nfrom .dataframe import from_pandas\nfrom .dataframe import to_pandas\nfrom .series import Series\n\n__all__ = [\"DataFrame\", \"from_pandas\", \"to_pandas\", \"Series\"]\n", "path": "python/ray/dataframe/__init__.py"}]}