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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 make_secure_channel(credentials, user_agent, host, extra_options=()):
 """Makes a secure channel for an RPC service. Uses / depends on gRPC. :type credentials: :class:`google.auth.credentials.Credentials` :param credentials: The OAuth2 Credentials to use for creating access tokens. :type user_agent: str :param user_agent: The user agent to be used with API requests. :type host: str :param host: The host for the service. :type extra_options: tuple :param extra_options: (Optional) Extra gRPC options used when creating the channel. :rtype: :class:`grpc._channel.Channel` :returns: gRPC secure channel with credentials attached. """

    target = "%s:%d" % (host, http_client.HTTPS_PORT)
    http_request = google.auth.transport.requests.Request()

    user_agent_option = ("grpc.primary_user_agent", user_agent)
    options = (user_agent_option,) + extra_options
    return google.auth.transport.grpc.secure_authorized_channel(
        credentials, http_request, target, options=options
    )