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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 process_ndex_network(network_id, username=None, password=None, require_grounding=True):
 """Process an NDEx network into Statements. Parameters network_id : str NDEx network ID. username : str NDEx username. password : str NDEx password. require_grounding: bool Whether network nodes lacking grounding information should be included among the extracted Statements (default is True). Returns ------- NdexCxProcessor Processor containing Statements. Returns None if there if the HTTP status code indicates an unsuccessful request. """

    nd = ndex2.client.Ndex2(username=username, password=password)
    res = nd.get_network_as_cx_stream(network_id)
    if res.status_code != 200:
        logger.error('Problem downloading network: status code %s' %
                     res.status_code)
        logger.error('Response: %s' % res.text)
        return None
    json_list = res.json()
    summary = nd.get_network_summary(network_id)
    return process_cx(json_list, summary=summary,
                      require_grounding=require_grounding)