concat = (objs: T_OBJS, kwargs: T_KWARGS = {ignore_index: false, axis: 0}): T_CONCAT => {
  if ((Array.isArray(objs) && objs[0] instanceof Series)
      || (objs instanceof Immutable.List && objs.get(0) instanceof Series))
    return _concatSeries(objs, {ignore_index: kwargs.ignore_index});
  else if ((Array.isArray(objs) && objs[0] instanceof DataFrame)
    || (objs instanceof Immutable.List && objs.get(0) instanceof DataFrame))
    return _concatDataFrame(objs, {ignore_index: kwargs.ignore_index, axis: kwargs.axis});
  throw new Error('Not supported');
}
Concatenate pandas objects along a particular axis.

pandas equivalent: [pandas.concat](https://pandas.pydata.org/pandas-docs/stable/generated/pandas.concat.html)

@returns {Series | DataFrame}

@example
const series1 = new Series([1, 2, 3, 4]);
const series2 = new Series([2, 3, 4, 5]);

// Returns Series([1, 2, 3, 4, 2, 3, 4, 5], {index: [0, 1, 2, 3, 0, 1, 2, 3]})
concat([series1, series2], {ignore_index: false});

// Returns Series([1, 2, 3, 4, 2, 3, 4, 5], {index: [0, 1, 2, 3, 4, 5, 6, 7]})
concat([series1, series2], {ignore_index: true});