function columnNames() {
	      return _columnNames.apply(this, arguments);
	    }
Returns column names of the csv dataset. If `configuredColumnsOnly` is
true, return column names in `columnConfigs`. If `configuredColumnsOnly` is
false and `columnNames` is provided, `columnNames`. If
`configuredColumnsOnly` is false and `columnNames` is not provided, return
all column names parsed from the csv file. For example usage please go to
`tf.data.csv`.

@doc {heading: 'Data', subheading: 'Classes'}