code: public static Configuration configure(Configuration conf, String projectId, String instanceId) {
      conf.set(BigtableOptionsFactory.PROJECT_ID_KEY, projectId);
      conf.set(BigtableOptionsFactory.INSTANCE_ID_KEY, instanceId);
      conf.set(HBASE_CLIENT_CONNECTION_IMPL, getConnectionClass().getCanonicalName());
      return conf;
    }
docs: <p>Configure and return an existing {@link org.apache.hadoop.conf.Configuration}.</p>
  
  @param conf a {@link org.apache.hadoop.conf.Configuration} object to configure.
  @param projectId a {@link java.lang.String} object.
  @param instanceId a {@link java.lang.String} object.
  @return the modified {@link org.apache.hadoop.conf.Configuration} object.