code: def test_line_comment(all_parsers, read_kwargs, request):
      parser = all_parsers
      data = """# empty
  A,B,C
  1,2.,4.#hello world
  #ignore this line
  5.,NaN,10.0
  """
      warn = None
      depr_msg = (
          "The 'delim_whitespace' keyword in pd.read_csv is deprecated"
      )
  
      if read_kwargs.get("delim_whitespace"):
          data = data.replace(",", " ")
          warn = FutureWarning
      elif read_kwargs.get("lineterminator"):
          data = data.replace("\n", read_kwargs.get("lineterminator"))
  
      read_kwargs["comment"] = "#"
      if parser.engine == "pyarrow":
          if "lineterminator" in read_kwargs:
              msg = "The 'lineterminator' option is not supported with the 'pyarrow' engine"
          else:
              msg = "The 'comment' option is not supported with the 'pyarrow' engine"
          with pytest.raises(ValueError, match=msg):
              with tm.assert_produces_warning(
                  warn, match=depr_msg, check_stacklevel=False
              ):
                  parser.read_csv(StringIO(data), **read_kwargs)
          return
      elif parser.engine == "python" and read_kwargs.get(
          "lineterminator"
      ):
          msg = r"Custom line terminators not supported in python parser \(yet\)"
          with pytest.raises(ValueError, match=msg):
              with tm.assert_produces_warning(
                  warn, match=depr_msg, check_stacklevel=False
              ):
                  parser.read_csv(StringIO(data), **read_kwargs)
          return
  
      with tm.assert_produces_warning(
          warn, match=depr_msg, check_stacklevel=False
      ):
          result = parser.read_csv(StringIO(data), **read_kwargs)
  
      expected = DataFrame(
          [[1.0, 2.0, 4.0], [5.0, np.nan, 10.0]],
          columns=["A", "B", "C"],
      )
      tm.assert_frame_equal(result, expected)
  
file_path: pandas/pandas/tests/io/parser/test_comment.py
imports: from io import StringIO
  import numpy
  import pytest
  from pandas import DataFrame
  import pandas._testing
label_desc: Use image node_id 2 for calling a global function with example usage: test_line_comment(all_parsers, read_kwargs, request) without return types