Add python api based ff cleanup demo

demo/feature_flag_cleanup_using_py_api/java/SampleClass.java

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+// Copyright (c) 2023 Uber Technologies, Inc.
+//
+// <p>Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
+// except in compliance with the License. You may obtain a copy of the License at
+// <p>http://www.apache.org/licenses/LICENSE-2.0
+//
+// <p>Unless required by applicable law or agreed to in writing, software distributed under the
+// License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+// express or implied. See the License for the specific language governing permissions and
+// limitations under the License.
+
+class SampleJava {
+
+  public void sampleMethod(ExperimentInterface exp) {
+    if (exp.isTreated("SAMPLE_STALE_FLAG")) {
+      System.out.println("SAMPLE_STALE_FLAG is enabled");
+    } else {
+      System.out.println("SAMPLE_STALE_FLAG is disabled");
+    }
+  }
+}

demo/stale_feature_flag_cleanup_demos_using_py_api.py

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+from os.path import join, dirname, getmtime, exists
+from polyglot_piranha import Rule, RuleGraph, execute_piranha, PiranhaArguments
+import logging
+from logging import info
+
+feature_flag_dir = join(dirname(__file__), "feature_flag_cleanup_using_py_api")
+
+
+def run_java_ff_demo():
+    info("Running the stale feature flag cleanup demo for Java")
+
+    directory_path = join(feature_flag_dir, "java")
+    modified_file_path = join(directory_path, "SampleClass.java")
+
+    update_is_treated = Rule(
+        name="update_is_treated",
+        # :[e] matches any node (its like a hole) and @flag_name refers to the substitution
+        query='cs :[e].isTreated("@flag_name")',
+        replace_node="*",
+        # @treated refers to the substitution
+        replace="@treated",
+        groups={"replace_expression_with_boolean_literal"},
+        # This is a list of holes that need to be filled in for the rule to be applied
+        holes={"treated", "flag_name"}
+    )
+
+    args = PiranhaArguments(
+        "java",
+        paths_to_codebase=[directory_path],
+        substitutions={"flag_name": "SAMPLE_STALE_FLAG", "treated": "true"},
+        rule_graph=RuleGraph(rules=[update_is_treated], edges=[])
+    )
+
+    output_summaries = execute_piranha(args)
+
+    old_mtime = getmtime(modified_file_path)
+
+    assert len(output_summaries) == 1
+
+    for summary in output_summaries:
+        assert len(summary.rewrites) > 0
+
+    new_mtime = getmtime(modified_file_path)
+
+    assert old_mtime < new_mtime
+
+
+FORMAT = "%(levelname)s %(name)s %(asctime)-15s %(filename)s:%(lineno)d %(message)s"
+logging.basicConfig(format=FORMAT)
+logging.getLogger().setLevel(logging.DEBUG)
+
+run_java_ff_demo()
+print("Completed running the stale feature flag cleanup demos")