code: def test_ea_categories():
      # GH 54300
      df = DataFrame(
          {"a": [1, 0, 0, 1], "b": [0, 1, 0, 0], "c": [0, 0, 1, 0]}
      )
      df.columns = df.columns.astype("string[python]")
      result = from_dummies(df)
      expected = DataFrame(
          {"": Series(list("abca"), dtype="string[python]")}
      )
      tm.assert_frame_equal(result, expected)
  
imports: import numpy
  import pytest
  from pandas import DataFrame, Series, from_dummies, get_dummies
  import pandas._testing
label_desc: Use image node_id 31 for calling a global function with example usage: test_ea_categories() without return types