Example of refactoring using rope library.

tools/telemetry/third_party/rope/rope/base/prefs.py

Index: tools/telemetry/third_party/rope/rope/base/prefs.py
diff --git a/tools/telemetry/third_party/rope/rope/base/prefs.py b/tools/telemetry/third_party/rope/rope/base/prefs.py
new file mode 100644
index 0000000000000000000000000000000000000000..2ab45dac541d9ef4150b81dcc65b7af08db770ca
--- /dev/null
+++ b/tools/telemetry/third_party/rope/rope/base/prefs.py
@@ -0,0 +1,41 @@
+class Prefs(object):
+
+    def __init__(self):
+        self.prefs = {}
+        self.callbacks = {}
+
+    def set(self, key, value):
+        """Set the value of `key` preference to `value`."""
+        if key in self.callbacks:
+            self.callbacks[key](value)
+        else:
+            self.prefs[key] = value
+
+    def add(self, key, value):
+        """Add an entry to a list preference
+
+        Add `value` to the list of entries for the `key` preference.
+
+        """
+        if not key in self.prefs:
+            self.prefs[key] = []
+        self.prefs[key].append(value)
+
+    def get(self, key, default=None):
+        """Get the value of the key preference"""
+        return self.prefs.get(key, default)
+
+    def add_callback(self, key, callback):
+        """Add `key` preference with `callback` function
+
+        Whenever `key` is set the callback is called with the
+        given `value` as parameter.
+
+        """
+        self.callbacks[key] = callback
+
+    def __setitem__(self, key, value):
+        self.set(key, value)
+
+    def __getitem__(self, key):
+        return self.get(key)