[DOC] cudf.DataFrame.merge how options incomplete

[ncclementi]

Report needed documentation and Describe the problems or issues found in the documentation

The documentation on cudf.DataFrame.merge more specifically the how part is incomplete. Docstrings are here

cudf/python/cudf/cudf/core/dataframe.py

Lines 4372 to 4381 in e597075

	how : {‘left’, ‘outer’, ‘inner’}, default ‘inner’
	Type of merge to be performed.
	- left : use only keys from left frame, similar to a SQL left
	outer join.
	- right : not supported.
	- outer : use union of keys from both frames, similar to a SQL
	full outer join.
	- inner: use intersection of keys from both frames, similar to
	a SQL inner join.

and for what I read in the Merge class here

cudf/python/cudf/cudf/core/join/join.py

Lines 115 to 117 in 34b54ca

	how : string
	The type of join. Possible values are
	'inner', 'outer', 'left', 'leftsemi' and 'leftanti'

we are missing leftsemi and leftanti on the merge documentation that will display in https://docs.rapids.ai/api/cudf/stable/api_docs/api/cudf.DataFrame.merge.html

Steps taken to verify documentation is incorrect
See dask/dask#8138 (review)

Suggested fix for documentation
"leftanti" and ""leftsemi should be added here:

cudf/python/cudf/cudf/core/dataframe.py

Lines 4372 to 4381 in e597075

	how : {‘left’, ‘outer’, ‘inner’}, default ‘inner’
	Type of merge to be performed.
	- left : use only keys from left frame, similar to a SQL left
	outer join.
	- right : not supported.
	- outer : use union of keys from both frames, similar to a SQL
	full outer join.
	- inner: use intersection of keys from both frames, similar to
	a SQL inner join.