detect_problem_type can't handle DataColumns

[freddyaboulton]

Repro

from evalml.problem_types import detect_problem_type
from evalml.demos import load_breast_cancer

X, y = load_breast_cancer()

detect_problem_type(y)

-----------------------------------------------------------------
TypeError                       Traceback (most recent call last)
<ipython-input-41-6bcb844deb7e> in <module>
----> 1 detect_problem_type(y)

~/sources/evalml/evalml/problem_types/utils.py in detect_problem_type(y)
     41     """
     42     y = pd.Series(y).dropna()
---> 43     num_classes = y.nunique()
     44     if num_classes < 2:
     45         raise ValueError("Less than 2 classes detected! Target unusable for modeling")

~/miniconda3/envs/evalml/lib/python3.8/site-packages/pandas/core/base.py in nunique(self, dropna)
   1301         4
   1302         """
-> 1303         uniqs = self.unique()
   1304         n = len(uniqs)
   1305         if dropna and isna(uniqs).any():

~/miniconda3/envs/evalml/lib/python3.8/site-packages/pandas/core/series.py in unique(self)
   1879         Categories (3, object): ['a' < 'b' < 'c']
   1880         """
-> 1881         result = super().unique()
   1882         return result
   1883 

~/miniconda3/envs/evalml/lib/python3.8/site-packages/pandas/core/base.py in unique(self)
   1263                     result = np.asarray(result)
   1264         else:
-> 1265             result = unique1d(values)
   1266 
   1267         return result

~/miniconda3/envs/evalml/lib/python3.8/site-packages/pandas/core/algorithms.py in unique(values)
    397 
    398     table = htable(len(values))
--> 399     uniques = table.unique(values)
    400     uniques = _reconstruct_data(uniques, original.dtype, original)
    401     return uniques

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.unique()

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable._unique()

TypeError: unhashable type: 'DataColumn'

I think the problem is that calling pd.Series on a DataColumn doesn't produce the type of series we're expecting.

[dsherry]

@tyler3991 says we're close on the new woodwork accessor API. So I'm tempted to punt on this until we've added that support. Because once we've updated, there won't even be a DataColumn anymore! I think it'll solve this problem implicitly. That's tracked by #1965