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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_host(environ):
 # type: (Dict[str, str]) -> str """Return the host for the given WSGI environment. Yanked from Werkzeug."""

    if environ.get("HTTP_HOST"):
        rv = environ["HTTP_HOST"]
        if environ["wsgi.url_scheme"] == "http" and rv.endswith(":80"):
            rv = rv[:-3]
        elif environ["wsgi.url_scheme"] == "https" and rv.endswith(":443"):
            rv = rv[:-4]
    elif environ.get("SERVER_NAME"):
        rv = environ["SERVER_NAME"]
        if (environ["wsgi.url_scheme"], environ["SERVER_PORT"]) not in (
            ("https", "443"),
            ("http", "80"),
        ):
            rv += ":" + environ["SERVER_PORT"]
    else:
        # In spite of the WSGI spec, SERVER_NAME might not be present.
        rv = "unknown"

    return rv