Usage
spark_connect(master, spark_home = Sys.getenv("SPARK_HOME"),
method = c("shell", "livy", "databricks", "test"), app_name = "sparklyr",
version = NULL, hadoop_version = NULL, config = spark_config(),
extensions = sparklyr::registered_extensions(), ...)spark_connection_is_open(sc)
spark_disconnect(sc, ...)
spark_disconnect_all()