code: def test_append():
      df1 = pd.DataFrame(np.random.rand(10, 4), columns=list("ABCD"))
      df2 = pd.DataFrame(np.random.rand(10, 4), columns=list("ABCD"))
  
      mdf1 = from_pandas(df1, chunk_size=3)
      mdf2 = from_pandas(df2, chunk_size=3)
      adf = mdf1.append(mdf2)
  
      assert adf.shape == (20, 4)
      assert isinstance(adf.index_value.value, IndexValue.Int64Index)
  
      tiled = tile(adf)
      assert tiled.nsplits == ((3, 3, 3, 1, 3, 3, 3, 1), (3, 1))
      assert tiled.chunk_shape == (8, 2)
      for i, c in enumerate(tiled.chunks):
          index = (i // 2, i % 2)
          assert c.index == index
  
      mdf1 = from_pandas(df1, chunk_size=3)
      mdf2 = from_pandas(df2, chunk_size=3)
      adf = mdf1.append(mdf2, ignore_index=True)
  
      assert adf.shape == (20, 4)
      assert isinstance(adf.index_value.value, IndexValue.RangeIndex)
      pd.testing.assert_index_equal(
          adf.index_value.to_pandas(), pd.RangeIndex(20)
      )
  
file_path: mars/mars/dataframe/merge/tests/test_merge.py
imports: import numpy
  import pandas
  import pytest
  from ....core import tile
  from ....core.operand import OperandStage
  from ...core import IndexValue
  from ...datasource.dataframe import from_pandas
  from ..None import DataFrameMergeAlign, DataFrameMerge, concat
label_desc: Use image node_id 6 for calling a global function with example usage: test_append() without return types