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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 sign_apk(filename, keystore, storepass):
 """ Use jarsigner to sign an APK file. :param filename: APK file on disk to sign (path) :param keystore: path to keystore :param storepass: your keystorage passphrase """

    from subprocess import Popen, PIPE, STDOUT
    # TODO use apksigner instead of jarsigner
    cmd = Popen([androconf.CONF["BIN_JARSIGNER"], "-sigalg", "MD5withRSA",
                 "-digestalg", "SHA1", "-storepass", storepass, "-keystore",
                 keystore, filename, "alias_name"],
                stdout=PIPE,
                stderr=STDOUT)
    stdout, stderr = cmd.communicate()