> TestFunc
function(flights) {
ans <- data.table:::`[.data.table`(flights,
                                 carrier == "AA",
                                 .(mean1 = mean(arr_delay), mean2 = mean(dep_delay)),
                                 by=.(origin, dest, month))
 return(ans)
}
<environment: namespace:rmypackage>
> flights <- data.table::fread("flights14.csv")
> TestFunc(flights = flights)
 Error in `[.data.frame`(x, i, j) : could not find function "."
Called from: `[.data.frame`(x, i, j)

> TestFunc <- function(flights) {
+   ans <- data.table:::`[.data.table`(flights,
+                                      carrier == "AA",
+                                      .(mean1 = mean(arr_delay), mean2 = mean(dep_delay)),
+                                      by=.(origin, dest, month))
+   return(ans)
+ }
> TestFunc(flights = flights)
 origin dest month      mean1      mean2
 1:    JFK  LAX     1   6.590361 14.2289157
 2:    LGA  PBI     1  -7.758621  0.3103448
 3:    EWR  LAX     1   1.366667  7.5000000
 4:    JFK  MIA     1  15.720670 18.7430168
 5:    JFK  SEA     1  14.357143 30.7500000
 ---
196:    LGA  MIA    10  -6.251799 -1.4208633
197:    JFK  MIA    10  -1.880184  6.6774194
198:    EWR  PHX    10  -3.032258 -4.2903226
199:    JFK  MCO    10 -10.048387 -1.6129032
200:    JFK  DCA    10  16.483871 15.5161290
>