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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def parse_requirements( filename, # type: str finder=None, # type: Optional[PackageFinder] comes_from=None, # type: Optional[str] options=None, # type: Optional[optparse.Values] session=None, # type: Optional[PipSession] constraint=False, # type: bool wheel_cache=None, # type: Optional[WheelCache] use_pep517=None # type: Optional[bool] ):
 """Parse a requirements file and yield InstallRequirement instances. :param filename: Path or url of requirements file. :param finder: Instance of pip.index.PackageFinder. :param comes_from: Origin description of requirements. :param options: cli options. :param session: Instance of pip.download.PipSession. :param constraint: If true, parsing a constraint file rather than requirements file. :param wheel_cache: Instance of pip.wheel.WheelCache :param use_pep517: Value of the --use-pep517 option. """

    if session is None:
        raise TypeError(
            "parse_requirements() missing 1 required keyword argument: "
            "'session'"
        )

    _, content = get_file_content(
        filename, comes_from=comes_from, session=session
    )

    lines_enum = preprocess(content, options)

    for line_number, line in lines_enum:
        req_iter = process_line(line, filename, line_number, finder,
                                comes_from, options, session, wheel_cache,
                                use_pep517=use_pep517, constraint=constraint)
        for req in req_iter:
            yield req