A function to compute the extra term that shows up in the influence function for aggregated treatment effect parameters due to estimating the weights
wif(keepers, pg, weights.ind, G, group)
a vector of indices for which group-time average treatment effects are used to compute a particular aggregated parameter
a vector with same length as total number of group-time average treatment effects that contains the probability of being in particular group
additional sampling weights (nx1)
vector containing which group a unit belongs to (nx1)
vector of groups
nxk influence function matrix