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argwhere does not work with pandas Series

See original GitHub issue

np.argwhere() does not work on a pandas series in v1.18.1, whereas it works in an older version v1.17.3. Also, np.where() works on a pandas series but np.argwhere() does not.

Reproducing code example:

import numpy as np
import pandas as pd

ser = pd.Series(np.random.randn(5), index=['a', 'b', 'c', 'd', 'e'])
np.argwhere(ser < 0)

Error message:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<__array_function__ internals>", line 6, in argwhere
  File "/Users/kramanathan/anaconda3/envs/py3.7/lib/python3.7/site-packages/numpy/core/numeric.py", line 584, in argwhere
    return transpose(nonzero(a))
  File "<__array_function__ internals>", line 6, in nonzero
  File "/Users/kramanathan/anaconda3/envs/py3.7/lib/python3.7/site-packages/numpy/core/fromnumeric.py", line 1896, in nonzero
    return _wrapfunc(a, 'nonzero')
  File "/Users/kramanathan/anaconda3/envs/py3.7/lib/python3.7/site-packages/numpy/core/fromnumeric.py", line 58, in _wrapfunc
    return _wrapit(obj, method, *args, **kwds)
  File "/Users/kramanathan/anaconda3/envs/py3.7/lib/python3.7/site-packages/numpy/core/fromnumeric.py", line 51, in _wrapit
    result = wrap(result)
  File "/Users/kramanathan/anaconda3/envs/py3.7/lib/python3.7/site-packages/pandas/core/generic.py", line 1918, in __array_wrap__
    return self._constructor(result, **d).__finalize__(self)
  File "/Users/kramanathan/anaconda3/envs/py3.7/lib/python3.7/site-packages/pandas/core/series.py", line 292, in __init__
    f"Length of passed values is {len(data)}, "
ValueError: Length of passed values is 1, index implies 5.