Update the `research` package to use the pip-style import.

* Updated the `research` package imports.
* Increased the BUILD visibility strictness.

PiperOrigin-RevId: 268692104

tensorflow_federated/BUILD

-package(default_visibility = ["//visibility:public"])
+package(default_visibility = ["//visibility:private"])
 
 licenses(["notice"])  # Apache 2.0
 
@@ -7,6 +7,7 @@ exports_files(["LICENSE"])
 py_library(
     name = "tensorflow_federated",
     srcs = ["__init__.py"],
+    visibility = ["//visibility:public"],
     deps = [
         ":version",
         "//tensorflow_federated/python/core/api:computation_base",

tensorflow_federated/python/research/baseline_fedavg/simple_fedavg.py

@@ -35,8 +35,8 @@ import collections
 
 import attr
 import tensorflow as tf
-
 import tensorflow_federated as tff
+
 from tensorflow_federated.python.tensorflow_libs import tensor_utils
 
 

tensorflow_federated/python/research/baseline_fedavg/simple_fedavg_test.py

@@ -22,8 +22,8 @@ import collections
 
 import numpy as np
 import tensorflow as tf
-
 import tensorflow_federated as tff
+
 from tensorflow_federated.python.examples.mnist import models
 from tensorflow_federated.python.research.baseline_fedavg import simple_fedavg
 from tensorflow_federated.python.research.baseline_fedavg.simple_fedavg import build_federated_averaging_process

tensorflow_federated/python/research/baselines/emnist/run_experiment.py

@@ -25,9 +25,9 @@ import attr
 import numpy as np
 import pandas as pd
 import tensorflow as tf
+import tensorflow_federated as tff
 
 from tensorboard.plugins.hparams import api as hp
-import tensorflow_federated as tff
 from tensorflow_federated.python.research import utils
 from tensorflow_federated.python.research.baselines.emnist import models
 from tensorflow_federated.python.research.utils import training_loops

tensorflow_federated/python/research/robust_aggregation/BUILD

@@ -5,7 +5,6 @@ licenses(["notice"])  # Apache 2.0
 py_library(
     name = "robust_aggregation",
     srcs = ["__init__.py"],
-    visibility = ["//visibility:public"],
     deps = [":robust_federated_aggregation"],
 )
 

tensorflow_federated/python/research/robust_aggregation/robust_federated_aggregation_test.py

@@ -17,8 +17,8 @@ import collections
 
 import numpy as np
 import tensorflow as tf
+import tensorflow_federated as tff
 
-from tensorflow_federated.python import core as tff
 from tensorflow_federated.python import learning
 from tensorflow_federated.python.common_libs import py_typecheck
 from tensorflow_federated.python.learning import model_utils

tensorflow_federated/python/research/utils/training_loops_test.py

@@ -17,8 +17,8 @@ import collections
 
 import numpy as np
 import tensorflow as tf
-
 import tensorflow_federated as tff
+
 from tensorflow_federated.python.examples.mnist import models
 from tensorflow_federated.python.research.utils import training_loops