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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_context_jar(self, compile_context):
 """Jar up the compile_context to its output jar location. TODO(stuhood):
 In the medium term, we hope to add compiler support for this step, which would allow the jars to be used as compile _inputs_ as well. Currently using jar'd compile outputs as compile inputs would make the compiler's analysis useless. see https://github.com/twitter-forks/sbt/tree/stuhood/output-jars """

    root = compile_context.classes_dir.path
    with compile_context.open_jar(mode='w') as jar:
      for abs_sub_dir, dirnames, filenames in safe_walk(root):
        for name in dirnames + filenames:
          abs_filename = os.path.join(abs_sub_dir, name)
          arcname = fast_relpath(abs_filename, root)
          jar.write(abs_filename, arcname)