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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 get_ecosystem_solver(ecosystem_name, parser_kwargs=None, fetcher_kwargs=None):
 """Get Solver subclass instance for particular ecosystem. :param ecosystem_name: name of ecosystem for which solver should be get :param parser_kwargs: parser key-value arguments for constructor :param fetcher_kwargs: fetcher key-value arguments for constructor :return: Solver """

    from .python import PythonSolver

    if ecosystem_name.lower() == "pypi":
        source = Source(url="https://pypi.org/simple", warehouse_api_url="https://pypi.org/pypi", warehouse=True)
        return PythonSolver(parser_kwargs, fetcher_kwargs={"source": source})

    raise NotImplementedError("Unknown ecosystem: {}".format(ecosystem_name))