code: @Override
      public void collect(ScriptFile scriptFile) {
          if (!versions.contains(scriptFile.getVersion())) {
              scripts.add(scriptFile);
              versions.add(scriptFile.getVersion());
          } else {
              throw new MigrationException(
                      format("Found two different files for version %d", scriptFile.getVersion()),
                      scriptFile.getScriptName());
          }
      }
docs: {@inheritDoc}
  
  Checks for every <code>scriptFile</code> that was added if there was
  already a script with the same version added. Throws an exception of
  it is the case.
  
  @param scriptFile an object containing information about the script. Never null.
  @throws MigrationException if a two different scripts with the same version are added