code: def test_dataframe_scatter_by_map_empty():
      df = DataFrame({"a": [], "b": []})
      scattered = df.scatter_by_map(df["a"])
      assert len(scattered) == 0
  
imports: import string
  from itertools import product
  import numpy
  import pandas
  import pytest
  from cudf import DataFrame, Series
  from cudf.core.column import NumericalColumn
  from cudf.testing._utils import DATETIME_TYPES, NUMERIC_TYPES, assert_eq, assert_exceptions_equal, expect_warning_if
label_desc: Use image node_id 19 for calling a global function with example usage: test_dataframe_scatter_by_map_empty() without return types