Integrate with gRPC.

def trace_grpc(tracer=None):
    """Integrate with gRPC."""
    # Wrap google.cloud._helpers.make_secure_channel
    make_secure_channel_func = getattr(_helpers, MAKE_SECURE_CHANNEL)
    make_secure_channel_wrapped = wrap_make_secure_channel(
        make_secure_channel_func, tracer)
    setattr(
        _helpers,
        MAKE_SECURE_CHANNEL,
        make_secure_channel_wrapped)

    # Wrap the grpc.insecure_channel.
    insecure_channel_func = getattr(grpc, INSECURE_CHANNEL)
    insecure_channel_wrapped = wrap_insecure_channel(
        insecure_channel_func, tracer)
    setattr(
        grpc,
        INSECURE_CHANNEL,
        insecure_channel_wrapped)

    # Wrap google.api_core.grpc_helpers.create_channel
    create_channel_func = getattr(grpc_helpers, CREATE_CHANNEL)
    create_channel_wrapped = wrap_create_channel(create_channel_func, tracer)
    setattr(
        grpc_helpers,
        CREATE_CHANNEL,
        create_channel_wrapped)