Pandas first(’2D’) with series with index with a null in the middle raises KeyError

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
File ~/opt/anaconda3/envs/pandas-dev/lib/python3.10/site-packages/pandas/_libs/index.pyx:548, in pandas._libs.index.DatetimeEngine.get_loc()

File pandas/_libs/hashtable_class_helper.pxi:2263, in pandas._libs.hashtable.Int64HashTable.get_item()

File pandas/_libs/hashtable_class_helper.pxi:2273, in pandas._libs.hashtable.Int64HashTable.get_item()

KeyError: 1523404800000000000

During handling of the above exception, another exception occurred:

KeyError                                  Traceback (most recent call last)
File ~/opt/anaconda3/envs/pandas-dev/lib/python3.10/site-packages/pandas/core/indexes/base.py:3803, in Index.get_loc(self, key, method, tolerance)
   3802 try:
-> 3803     return self._engine.get_loc(casted_key)
   3804 except KeyError as err:

File ~/opt/anaconda3/envs/pandas-dev/lib/python3.10/site-packages/pandas/_libs/index.pyx:516, in pandas._libs.index.DatetimeEngine.get_loc()

File ~/opt/anaconda3/envs/pandas-dev/lib/python3.10/site-packages/pandas/_libs/index.pyx:550, in pandas._libs.index.DatetimeEngine.get_loc()

KeyError: Timestamp('2018-04-11 00:00:00')

The above exception was the direct cause of the following exception:

KeyError                                  Traceback (most recent call last)
File ~/opt/anaconda3/envs/pandas-dev/lib/python3.10/site-packages/pandas/core/indexes/datetimes.py:736, in DatetimeIndex.get_loc(self, key, method, tolerance)
    735 try:
--> 736     return Index.get_loc(self, key, method, tolerance)
    737 except KeyError as err:

File ~/opt/anaconda3/envs/pandas-dev/lib/python3.10/site-packages/pandas/core/indexes/base.py:3805, in Index.get_loc(self, key, method, tolerance)
   3804 except KeyError as err:
-> 3805     raise KeyError(key) from err
   3806 except TypeError:
   3807     # If we have a listlike key, _check_indexing_error will raise
   3808     #  InvalidIndexError. Otherwise we fall through and re-raise
   3809     #  the TypeError.

KeyError: Timestamp('2018-04-11 00:00:00')

The above exception was the direct cause of the following exception:

KeyError                                  Traceback (most recent call last)
Cell In [1], line 10
      8 print(ts.first('1D'))
      9 # raises KeyError
---> 10 print(ts.first('2D'))

File ~/opt/anaconda3/envs/pandas-dev/lib/python3.10/site-packages/pandas/core/generic.py:8946, in NDFrame.first(self, offset)
   8943     end = self.index.searchsorted(end_date, side="left")
   8944     return self.iloc[:end]
-> 8946 return self.loc[:end]

File ~/opt/anaconda3/envs/pandas-dev/lib/python3.10/site-packages/pandas/core/indexing.py:1073, in _LocationIndexer.__getitem__(self, key)
   1070 axis = self.axis or 0
   1072 maybe_callable = com.apply_if_callable(key, self.obj)
-> 1073 return self._getitem_axis(maybe_callable, axis=axis)

File ~/opt/anaconda3/envs/pandas-dev/lib/python3.10/site-packages/pandas/core/indexing.py:1290, in _LocIndexer._getitem_axis(self, key, axis)
   1288 if isinstance(key, slice):
   1289     self._validate_key(key, axis)
-> 1290     return self._get_slice_axis(key, axis=axis)
   1291 elif com.is_bool_indexer(key):
   1292     return self._getbool_axis(key, axis=axis)

File ~/opt/anaconda3/envs/pandas-dev/lib/python3.10/site-packages/pandas/core/indexing.py:1324, in _LocIndexer._get_slice_axis(self, slice_obj, axis)
   1321     return obj.copy(deep=False)
   1323 labels = obj._get_axis(axis)
-> 1324 indexer = labels.slice_indexer(slice_obj.start, slice_obj.stop, slice_obj.step)
   1326 if isinstance(indexer, slice):
   1327     return self.obj._slice(indexer, axis=axis)

File ~/opt/anaconda3/envs/pandas-dev/lib/python3.10/site-packages/pandas/core/indexes/datetimes.py:809, in DatetimeIndex.slice_indexer(self, start, end, step, kind)
    801 # GH#33146 if start and end are combinations of str and None and Index is not
    802 # monotonic, we can not use Index.slice_indexer because it does not honor the
    803 # actual elements, is only searching for start and end
    804 if (
    805     check_str_or_none(start)
    806     or check_str_or_none(end)
    807     or self.is_monotonic_increasing
    808 ):
--> 809     return Index.slice_indexer(self, start, end, step, kind=kind)
    811 mask = np.array(True)
    812 deprecation_mask = np.array(True)

File ~/opt/anaconda3/envs/pandas-dev/lib/python3.10/site-packages/pandas/core/indexes/base.py:6602, in Index.slice_indexer(self, start, end, step, kind)
   6559 """
   6560 Compute the slice indexer for input labels and step.
   6561
   (...)
   6598 slice(1, 3, None)
   6599 """
   6600 self._deprecated_arg(kind, "kind", "slice_indexer")
-> 6602 start_slice, end_slice = self.slice_locs(start, end, step=step)
   6604 # return a slice
   6605 if not is_scalar(start_slice):

File ~/opt/anaconda3/envs/pandas-dev/lib/python3.10/site-packages/pandas/core/indexes/base.py:6816, in Index.slice_locs(self, start, end, step, kind)
   6814 end_slice = None
   6815 if end is not None:
-> 6816     end_slice = self.get_slice_bound(end, "right")
   6817 if end_slice is None:
   6818     end_slice = len(self)

File ~/opt/anaconda3/envs/pandas-dev/lib/python3.10/site-packages/pandas/core/indexes/base.py:6729, in Index.get_slice_bound(self, label, side, kind)
   6726         return self._searchsorted_monotonic(label, side)
   6727     except ValueError:
   6728         # raise the original KeyError
-> 6729         raise err
   6731 if isinstance(slc, np.ndarray):
   6732     # get_loc may return a boolean array, which
   6733     # is OK as long as they are representable by a slice.
   6734     assert is_bool_dtype(slc.dtype)

File ~/opt/anaconda3/envs/pandas-dev/lib/python3.10/site-packages/pandas/core/indexes/base.py:6723, in Index.get_slice_bound(self, label, side, kind)
   6721 # we need to look up the label
   6722 try:
-> 6723     slc = self.get_loc(label)
   6724 except KeyError as err:
   6725     try:

File ~/opt/anaconda3/envs/pandas-dev/lib/python3.10/site-packages/pandas/core/indexes/datetimes.py:738, in DatetimeIndex.get_loc(self, key, method, tolerance)
    736     return Index.get_loc(self, key, method, tolerance)
    737 except KeyError as err:
--> 738     raise KeyError(orig_key) from err

KeyError: Timestamp('2018-04-11 00:00:00')