code: public void deleteColumns(String storeName, String rowKey, Collection<String> columnNames) {
          for(String columnName: columnNames) {
              deleteColumn(storeName, rowKey, columnName);
          }
      }
docs: Add updates that will delete all given columns names for the given store name and
  row key. If a column update exists for the same store/row/column, the results are
  undefined when the transaction is committed.
  
  @param storeName Name of store that owns row.
  @param rowKey    Row key in string form.
  @param columnNames  Collection of column names in string form.