Modify build file visibility

PiperOrigin-RevId: 455649697

Author: tensorflower-gardener

Diff for: research/pate_2018/BUILD

@@ -1,4 +1,6 @@
-package(default_visibility = ["//visibility:private"])
+load("@rules_python//python:defs.bzl", "py_library")
+
+package(default_visibility = ["//visibility:public"])
 
 licenses(["notice"])
 
@@ -12,3 +14,8 @@ filegroup(
     ],
     tags = ["ignore_srcs"],
 )
+
+py_library(
+    name = "core",
+    srcs = ["core.py"],
+)