[ENH] Merge TsGroup?

[qian-chu]

In quite a few scenarios one may want to merge some TsGroup (e.g. adding new neurons, merging PETH from different runs, etc.) but currently TsGroup is non-mutable:

pynapple/pynapple/core/ts_group.py

Lines 149 to 151 in ea60357

	def __setitem__(self, key, value):
	if self._initialized:
	raise RuntimeError("TsGroup object is not mutable.")

Maybe we can add a method that takes two TsGroups and returns a new TsGroup when the following conditions are met:

1. Non-overlapping indices
2. Same meta-info columns
3. Same time support (if none specified, infer from start and end of the merged Ts/Tsd

Happy to initiate a pull request if people see a need for this.

[gviejo]

Hi Qian Chu, I think it's doable with the condition you just listed. Maybe a class method that does something like this

tsgroup = nap.TsGroup.join_group_set([tsgroup1, tsgroup2, tsgroup3])

Maybe this class method can be called by a simple method of TsGroup like this as well.

tsgroup = tsgroup1.join(tsgroup2)

In general I like to provide multiple ways of doing the same thing in pynapple. I noticed people have different intuition about how the package should behave.

Happy to review a PR.

[gviejo]

Solved in #275