docs: def check_regs(region_df, chr_name=None, start_name=None, stop_name=None,
                 strand_name=None, sample_name=None):
      """ Modifies a region dataframe to be coherent with the GMQL data model
  
      :param region_df: a pandas Dataframe of regions that is coherent with the GMQL data model
      :param chr_name: (optional) which column of :attr:`~.region_df` is the chromosome
      :param start_name: (optional) which column of :attr:`~.region_df` is the start
      :param stop_name: (optional) which column of :attr:`~.region_df` is the stop
      :param strand_name: (optional) which column of :attr:`~.region_df` is the strand
      :return: a modified pandas Dataframe
      """
  
      if sample_name is None:
          region_df.index = np.repeat(default_id_sample, len(region_df))
      else:
          region_df = search_column(region_df, id_sample_aliases,
                                    id_sample_types, 'id_sample', sample_name)
          region_df = region_df.set_index("id_sample", drop=True)
          region_df = region_df.sort_index()
  
      region_df = search_column(region_df,  chr_aliases, chr_types, 'chr', chr_name)
      region_df = search_column(region_df, start_aliases, start_types, 'start', start_name)
      region_df = search_column(region_df, stop_aliases, stop_types, 'stop', stop_name)
      region_df = search_column(region_df, strand_aliases, strand_types, 'strand', strand_name)
      return region_df