code: def test_single_line(python_parser_only):
      # see gh-6607: sniff separator
      parser = python_parser_only
      result = parser.read_csv(
          StringIO("1,2"), names=["a", "b"], header=None, sep=None
      )
  
      expected = DataFrame({"a": [1], "b": [2]})
      tm.assert_frame_equal(result, expected)
  
imports: from __future__ import annotations
  import csv
  from io import BytesIO, StringIO, TextIOWrapper
  from typing import TYPE_CHECKING
  import numpy
  import pytest
  from pandas.errors import ParserError, ParserWarning
  from pandas import DataFrame, Index, MultiIndex
  import pandas._testing
label_desc: Use image node_id 7 for calling a global function with example usage: test_single_line(python_parser_only) without return types