code: def create_index(column_names, unique=False):
      
      connection = _State.connection()
      _State.reflect_metadata()
      table_name = _State.table.name
  
      table = _State.table
  
      index_name = re.sub(r'[^a-zA-Z0-9]', '', table_name) + '_'
      index_name += '_'.join(re.sub(r'[^a-zA-Z0-9]', '', x)
                             for x in column_names)
  
      if unique:
          index_name += '_unique'
  
      columns = []
      for column_name in column_names:
          columns.append(table.columns[column_name])
  
      current_indices = [x.name for x in table.indexes]
      index = sqlalchemy.schema.Index(index_name, *columns, unique=unique)
      if index.name not in current_indices:
          index.create(bind=_State.engine)
docs: Create a new index of the columns in column_names, where column_names is
      a list of strings. If unique is True, it will be a
      unique index.