code: def test_concat_axis0(self):
      # frame
      res = pd.concat([self.gdf, self.gdf])
      assert res.shape == (6, 2)
      assert isinstance(res, GeoDataFrame)
      assert isinstance(res.geometry, GeoSeries)
      self._check_metadata(res)
      exp = GeoDataFrame(
          pd.concat([pd.DataFrame(self.gdf), pd.DataFrame(self.gdf)])
      )
      assert_geodataframe_equal(exp, res)
  
      # series
      res = pd.concat([self.gdf.geometry, self.gdf.geometry])
      assert res.shape == (6,)
      assert isinstance(res, GeoSeries)
      assert isinstance(res.geometry, GeoSeries)
  
file_path: geopandas/geopandas/tests/test_merge.py
imports: import warnings
  import pandas
  import pyproj
  import pytest
  from geopandas._compat import PANDAS_GE_21
  from geopandas.testing import assert_geodataframe_equal
  from pandas.testing import assert_index_equal
  from shapely.geometry import Point
  from geopandas import GeoDataFrame, GeoSeries
label_desc: Use image node_id 4 for calling the TestMerging obj's underlying member method code with example usage: obj.test_concat_axis0() without return types