# Buggy code
def __call__(self, df):
    if self.col_names is not None:
        # if col_names is a list, return a DataFrame, else return a Series
        if isinstance(self._col_names, list):
            dtypes = df.dtypes[self._col_names]
            columns = parse_index(pd.Index(self._col_names), store_data=True)
            return self.new_dataframe(
                [df],
                shape=(df.shape[0], len(self._col_names)),
                dtypes=dtypes,
                index_value=df.index_value,
                columns_value=columns,
            )
        else:
            dtype = df.dtypes[self._col_names]
            return self.new_series(
                [df],
                shape=(df.shape[0],),
                dtype=dtype,
                index_value=df.index_value,
                name=self._col_names,
            )
    else:
        if isinstance(self.mask, SERIES_TYPE):
            index_value = parse_index(
                pd.Index([], dtype=df.index_value.to_pandas().dtype),
                key=tokenize(
                    df.key, self.mask.key, df.index_value.key, self.mask.index_value.key
                ),
            )
            return self.new_dataframe(
                [df, self._mask],
                shape=(np.nan, df.shape[1]),
                dtypes=df.dtypes,
                index_value=index_value,
                columns_value=df.columns,
            )
        else:
            index_value = parse_index(
                pd.Index([], dtype=df.index_value.to_pandas().dtype),
                key=tokenize(
                    df.key,
                    pd.util.hash_pandas_object(self.mask),
                    df.index_value.key,
                    parse_index(self.mask.index).key,
                ),
            )
            return self.new_dataframe(
                [df],
                shape=(np.nan, df.shape[1]),
                dtypes=df.dtypes,
                index_value=index_value,
                columns_value=df.columns,
            )


# Traceback (Exception)
In [28]: df = md.DataFrame(np.random.rand(10, 2))

In [29]: df + np.random.rand(10, 2)
---------------------------------------------------------------------------
Exception                                 Traceback (most recent call last)
<ipython-input-29-4a212df011a8> in <module>
----> 1 df + np.random.rand(10, 2)

~/Documents/mars_dev/mars/mars/dataframe/utils.py in wrapper(*args, **kwargs)
613     def wrapper(*args, **kwargs):
614         try:
--> 615             return func(*args, **kwargs)
616         except NotImplementedError:
617             return NotImplemented

~/Documents/mars_dev/mars/mars/dataframe/arithmetic/add.py in add(df, other, axis, level, fill_value)
33
34 def add(df, other, axis='columns', level=None, fill_value=None):
---> 35     other = wrap_sequence(other)
36     op = DataFrameAdd(axis=axis, level=level, fill_value=fill_value, lhs=df, rhs=other)
37     return op(df, other)

~/Documents/mars_dev/mars/mars/dataframe/utils.py in wrap_sequence(seq)
606
607     if isinstance(seq, (list, tuple, np.ndarray, TENSOR_TYPE)):
--> 608         seq = Series(seq)
609     return seq
610

~/Documents/mars_dev/mars/mars/dataframe/initializer.py in __init__(self, data, index, dtype, name, copy, chunk_size, gpu, sparse)
46             series = data
47         else:
---> 48             pd_series = pd.Series(data, index=index, dtype=dtype, name=name, copy=copy)
49             series = from_pandas_series(pd_series, chunk_size=chunk_size, gpu=gpu, sparse=sparse)
50         super(Series, self).__init__(series.data)

~/miniconda3/lib/python3.7/site-packages/pandas/core/series.py in __init__(self, data, index, dtype, name, copy, fastpath)
312                     data = data.copy()
313             else:
--> 314                 data = sanitize_array(data, index, dtype, copy, raise_cast_failure=True)
315
316                 data = SingleBlockManager(data, index, fastpath=True)

~/miniconda3/lib/python3.7/site-packages/pandas/core/internals/construction.py in sanitize_array(data, index, dtype, copy, raise_cast_failure)
727     elif subarr.ndim > 1:
728         if isinstance(data, np.ndarray):
--> 729             raise Exception("Data must be 1-dimensional")
730         else:
731             subarr = com.asarray_tuplesafe(data, dtype=dtype)

Exception: Data must be 1-dimensional

# Fixed code
def __call__(self, df):
    if self.col_names is not None:
        # if col_names is a list, return a DataFrame, else return a Series
        if isinstance(self._col_names, list):
            dtypes = df.dtypes[self._col_names]
            columns = parse_index(pd.Index(self._col_names), store_data=True)
            return self.new_dataframe(
                [df],
                shape=(df.shape[0], len(self._col_names)),
                dtypes=dtypes,
                index_value=df.index_value,
                columns_value=columns,
            )
        else:
            dtype = df.dtypes[self._col_names]
            return self.new_series(
                [df],
                shape=(df.shape[0],),
                dtype=dtype,
                index_value=df.index_value,
                name=self._col_names,
            )
    else:
        if isinstance(self.mask, SERIES_TYPE):
            index_value = parse_index(
                pd.Index([], dtype=df.index_value.to_pandas().dtype),
                key=tokenize(
                    df.key, self.mask.key, df.index_value.key, self.mask.index_value.key
                ),
            )
            return self.new_dataframe(
                [df, self._mask],
                shape=(np.nan, df.shape[1]),
                dtypes=df.dtypes,
                index_value=index_value,
                columns_value=df.columns_value,
            )
        else:
            index_value = parse_index(
                pd.Index([], dtype=df.index_value.to_pandas().dtype),
                key=tokenize(
                    df.key,
                    pd.util.hash_pandas_object(self.mask),
                    df.index_value.key,
                    parse_index(self.mask.index).key,
                ),
            )
            return self.new_dataframe(
                [df],
                shape=(np.nan, df.shape[1]),
                dtypes=df.dtypes,
                index_value=index_value,
                columns_value=df.columns_value,
            )