code: private static TransportChannelProvider buildChannelProvider(String endpoint,
        BigtableOptions options) {
  
      return defaultGrpcTransportProviderBuilder()
          .setEndpoint(endpoint)
          .setPoolSize(options.getChannelCount())
          .setChannelConfigurator(new ApiFunction<ManagedChannelBuilder, ManagedChannelBuilder>() {
            @Override
            public ManagedChannelBuilder apply(ManagedChannelBuilder channelBuilder) {
              return channelBuilder.usePlaintext();
            }
          })
          .build();
    }
docs: Creates {@link TransportChannelProvider} based on Channel Negotiation type.