add import methods in NAMESPACE

R-package/DESCRIPTION

@@ -12,5 +12,5 @@ BugReports: https://github.com/tqchen/xgboost/issues
 Depends:
     R (>= 2.0.2)
 Imports:
-    Matrix (>= 1.1-0), methods
-
+    Matrix (>= 1.1-0),
+    methods

R-package/NAMESPACE

@@ -10,5 +10,6 @@ export(xgb.save)
 export(xgb.train)
 export(xgboost)
 exportMethods(predict)
+import(methods)
 importClassesFrom(Matrix,dgCMatrix)
 importClassesFrom(Matrix,dgeMatrix)

R-package/R/utils.R

@@ -1,4 +1,5 @@
 #' @importClassesFrom Matrix dgCMatrix dgeMatrix
+#' @import methods
 
 # depends on matrix
 .onLoad <- function(libname, pkgname) {