ERR: MultiIndex searchsorted
 - [ ] closes #14833 
 - [ ] tests added / passed
 - [ ] passes ``git diff upstream/master | flake8 --diff``
 - [ ] whatsnew entry

@ShaharBental on the issue I indicated that this should simply raise a ``NotImplementedError`` (or maybe a ``ValueError``). I don't think this is actually useful as the indexing methods on a ``MultiIndex`` already do this (they use ``searchsorted`` internally in certain cases). ## [Current coverage](https://codecov.io/gh/pandas-dev/pandas/pull/14990?src=pr) is 84.66% (diff: 100%)
> Merging [#14990](https://codecov.io/gh/pandas-dev/pandas/pull/14990?src=pr) into [master](https://codecov.io/gh/pandas-dev/pandas/branch/master?src=pr) will increase coverage by **<.01%**

```diff
@@             master     #14990   diff @@
==========================================
  Files           144        144          
  Lines         51056      51072    +16   
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
+ Hits          43225      43241    +16   
  Misses         7831       7831          
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [aba7d25...d22e816](https://codecov.io/gh/pandas-dev/pandas/compare/aba7d255a165bbc221be106839c59a876655c0c2...d22e816034416a1e3ba314b9629c40027a4d0905?src=pr) @jreback Sorry, changed it to simply raise a NotImplementedError
I think it should be NotImplementedError and not ValueError, as the problem lies with the type of self and not any specific value. pls add a note in other api changes in 0.20.0 closing as stale. please ping if you'd like to continue.