code: public static Map<String, Object> getDimKeyFromRow(Collection<DimensionSpec> dimensions, Row row)
    {
  
      Map<String, Object> key = new HashMap<>();
      Map<String, Object> event = ((MapBasedRow) row).getEvent();
  
      for (DimensionSpec dimension : dimensions) {
        key.put(dimension.getOutputName(), event.get(dimension.getOutputName()));
      }
  
      return key;
    }
docs: @param dimensions A list of DimensionSpec in the specified in the query
  @param row        The Row to be used for looking up dimension values
  
  @return A Map of dimension/value from the row