code: public Statistics columnStats(String columnName, ColumnStats columnStats) {
  		Map<String, String> map = normalizeColumnStats(columnStats);
  		this.columnStats.put(columnName, map);
  		return this;
  	}
docs: Sets statistics for a column. Overwrites all existing statistics for this column.
  
  @param columnName  the column name
  @param columnStats expected statistics for the column