Susetting operator for Spark dataframe allowing a subset of column(s) to be selected using syntaxes similar to those supported by R dataframes
# S3 method for tbl_spark
[(x, i)
The Spark dataframe
Expression specifying subset of column(s) to include or exclude from the result (e.g., `["col1"]`, `[c("col1", "col2")]`, `[1:10]`, `[-1]`, `[NULL]`, or `[]`)