BUG: TypeError: data type 'string' not understood

[codingl2k1]

Describe the bug

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To Reproduce

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import xorbits.pandas as pd
pdf = pd.DataFrame({"A":[1, 2, 3], "B": [["1"], ["2"], ["3"]]})
pdf["B"].map(lambda x: x[0], dtype="string")

Traceback (most recent call last):
  File "/Users/codingl2k1/Work/xorbits/python/xorbits/pandas/mars_adapters/core.py", line 179, in wrapped
    return from_mars(c(*new_args, **new_kwargs))
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/codingl2k1/Work/xorbits/python/xorbits/_mars/dataframe/base/map.py", line 275, in series_map
    return op(series, dtype=dtype, skip_infer=skip_infer)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/codingl2k1/Work/xorbits/python/xorbits/_mars/core/mode.py", line 78, in _inner
    return func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/Users/codingl2k1/Work/xorbits/python/xorbits/_mars/dataframe/base/map.py", line 112, in __call__
    dtype = np.dtype(dtype)
            ^^^^^^^^^^^^^^^
TypeError: data type 'string' not understood

xorbits.pandas should support pd dtypes: https://pandas.pydata.org/docs/user_guide/text.html

1. Your Python version
2. The version of Xorbits you use
3. Versions of crucial packages, such as numpy, scipy and pandas
4. Full stack of the error.
5. Minimized code to reproduce the error.

Expected behavior

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Additional context

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