pandas.Index.get_indexer_for
- 
Index.get_indexer_for(target, **kwargs)[source] - 
Guaranteed return of an indexer even when non-unique.
This dispatches to get_indexer or get_indexer_nonunique as appropriate.
 
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Licensed under the 3-clause BSD License.
    https://pandas.pydata.org/pandas-docs/version/0.24.2/reference/api/pandas.Index.get_indexer_for.html