def METHOD_NAME(
    self,
    input_string,
    template_string=None,
    blank_msgstr=False,
    duplicate_style="msgctxt",
    success_expected=True,
):
    """Helper that converts to target format without using files."""
    input_file = BytesIO(input_string.encode())
    output_file = BytesIO()
    template_file = None
    if template_string:
        template_file = BytesIO(template_string.encode())
    expected_result = 1 if success_expected else 0
    converter = self.ConverterClass(
        input_file, output_file, template_file, blank_msgstr, duplicate_style
    )
    assert converter.run() == expected_result
    return converter.target_store, output_file