when multiple vcs are specified in `participants_matrix`, only the last will be effective

[zhiqiangxu]

According to the code:

ethereum-package/src/package_io/input_parser.star

Lines 545 to 548 in c56fd46

	for index, participant in enumerate(participants):
	for vc in vc_matrix:
	for k, v in vc.items():
	participants[index][k] = v

when multiple vcs are specified in participants_matrix, only the last will be effective since it'll override previous ones.

[GlacierWalrus]

@zhiqiangxu Are you certain that's not just copying the attributes for that particular vc? As I understand it, each participant is at most one el, cv, and vc, and if you want multiple vc's you would need to add additional participants. i.e. k is not the vc, but an attribute of the vc, e.g. vc.image

[zhiqiangxu]

@zhiqiangxu , here el_matrix/cl_matrix/vc_matrix are from the participants_matrix field and are all supposed to be a list.

Each vc in vc_matrix has the same attributes(e.g, vc_type), so the loop here is actually updating each participant with the same attributes(e.g, vc_type), so in the end only the last one will be effective.