def set_http_header(key, value, scheme=None, host=None, port=None):
    """ Add an HTTP header for all future requests. If a `host_port` is
    specified, this header will only be included in requests to that
    destination.

    :arg key: name of the HTTP header
    :arg value: value of the HTTP header
    :arg scheme:
    :arg host:
    :arg port:
    """
    address_key = (scheme, host, port)
    if address_key in _http_headers:
        _http_headers[address_key].append((key, value))
    else:
        _http_headers[address_key] = [(key, value)]
dataset/ETHPy150Open nigelsmall/py2neo/py2neo/database/http.py/set_http_header/original