Tablecloth bind for grouped datasests

	A	B	C	D	G	H	I	L	M
1	https://github.com/scicloj/tablecloth/issues/44
2
3
4	ds1				ds2
5
6	:x	:y			:x			:x	:y
7	A	1			A			A	1
8	A	2			A			A	2
9	B	3			C			A	5
10	B	4			C			B	3
11	A	5			C			B	4
12	B	6			A			B	6
13								A
14								A
15								A
16	(tablecloth/group-by ds1 [:x])				(tablecloth/group-by ds2 [:x])			C
17								C
18	group-id	name	data		group-id	name	data	C
19
20	0	{:x "A"}	:x	:y	0	{:x "A"}	:x
21			A	1			A
22			A	2			A
23			A	5			A
24
25	1	{:x "B"}	:x	:y	1	{:x "C"}	:x
26			B	3			C
27			B	4			C
28			B	6			C
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34	(tablecloth/bind (tablecloth/group-by ds1 [:x]) (tablecloth/group-by ds2 [:x]))
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38	group-id	name	data
39						possible implementation (need to be tested on various scenarios): ungroup, bind, group again
40	0	{:x "A"}	:x	:y
41			A	1
42			A	2		:x	:y
43			A	5		A	1
44			A			A	2
45			A			A	5
46			A			B	3
47						B	4
48	1	{:x "B"}	:x	:y		B	6
49			B	3		A
50			B	4		A
51			B	6		A
52						C
53	2	{:x "C"}	:x	:y		C
54			C			C
55			C
56			C
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