import requests
from gis_metadata.iso_metadata_parser import IsoParser
from gis_metadata.utils import COMPLEX_DEFINITIONS, CONTACTS, format_xpaths, ParserProperty
from xml.etree import cElementTree as ET

url = 'https://ebas-oai-pmh.nilu.no/oai/provider?verb=GetRecord&metadataPrefix=iso19115&identifier=oai:ebas-oai-pmh.nilu.no:SK0007R.19991231070000.20181210133000.filter_1pack..aerosol.52w.1w.SK01L_f1p_hm_07.SK01L_GF_AAS.lev2.nc'

response = requests.get(url)

#OAI-PMH/metadata
xml = response.content.decode('utf-8')
root = ET.fromstring(xml)
# Get content that is defined as the iso metadata
metadata = ET.tostring(root[2][0][1][0])

class CustomIsoParser(IsoParser):

    def _init_data_map(self):
        super(CustomIsoParser, self)._init_data_map()

        dataset_url_prop = 'metadata_dataset_url'
        self._data_map[dataset_url_prop] = 'identificationInfo/SV_ServiceIdentification/containsOperations/SV_OperationMetadata/connectPoint/CI_OnlineResource/linkage/URL'

        self._metadata_props.add(dataset_url_prop)

custom_iso_from_file = CustomIsoParser(metadata)

dataset_urls = custom_iso_from_file.metadata_dataset_url

print(dataset_urls)