def remove_entity_headers(headers, allowed=("expires", "content-location")):
    """Remove all entity headers from a list or :class:`Headers` object.  This
    operation works in-place.  `Expires` and `Content-Location` headers are
    by default not removed.  The reason for this is :rfc:`2616` section
    10.3.5 which specifies some entity headers that should be sent.

    .. versionchanged:: 0.5
       added `allowed` parameter.

    :param headers: a list or :class:`Headers` object.
    :param allowed: a list of headers that should still be allowed even though
                    they are entity headers.
    """
    allowed = set(x.lower() for x in allowed)
    headers[:] = [
        (key, value)
        for key, value in headers
        if not is_entity_header(key) or key.lower() in allowed
    ]