how to establish a rule in which 1 out of 2 array index must be present?

[musaev-haybulla]

How is it possible to implement such a check:
If there are products, then there must be 1 out of 2 indices - positive or negative, for example

products is absent - true
products[negative] = [1,2,3] -? true
products[positive] = [4,5,6] -> true
products[negative] = [1,2,3] AND products[positive] = [4,5,6] -> true
products[blablabla] = [4,5,6] -> false (fail index)
products - false (nothing index)