Need importClassesFrom(methods, "[") after removing blanket import(methods) (#6001)

* need importClassesFrom

* revert methods:: change, not necessary

Author: MichaelChirico

NAMESPACE

@@ -2,6 +2,7 @@ useDynLib("data_table", .registration=TRUE)
 
 ## For S4-ization
 importFrom(methods, "S3Part<-", slotNames)
+importMethodsFrom(methods, "[")
 exportClasses(data.table, IDate, ITime)
 ##