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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def create_jar_builder(self, jar):
 """Creates a ``JarTask.JarBuilder`` ready for use. This method should be called during in `execute` context and only after ensuring `JarTask.JarBuilder.prepare` has already been called in `prepare` context. :param jar: An opened ``pants.backend.jvm.tasks.jar_task.Jar`. """

    builder = self.JarBuilder(self.context, jar)
    yield builder
    builder.commit_manifest(jar)