code: protected final Split prepare(List<String> sqls) {
  		if (!sqls.isEmpty()) {
  			sqlNormalizer = sqls.size() == 1 ? new SqlNormalizer(sqls.get(0)) : new SqlNormalizer(sqls);
  			sqlCmdLabel = prefix + ".sql." + sqlNormalizer.getType();
  			return startSplit();
  		} else {
  			return null;
  		}
  	}
docs: Called before each SQL command execution. Prepares (obtains and starts) {@link org.javasimon.Stopwatch Stopwatch Simon}
  for measure bach SQL operations.
  
  @param sqls list of sql commands
  @return Simon stopwatch object or null if sql is null or empty