upl is a list of delegation data (named operator_param with token, owner and operator), either to add or remove an operator to a token and owner. It fails if the caller is not the declared owner in upl.
Transfers token ownerships specified in txs, a list of transfer_param (from, to, token). If caller is not the token owner, it must be declared in operator to be able to transfer, otherwise it fails.
Returns the list a token balance for each token id in requests.