Add option to read thresholds from FEWS xml

[martinvonk]

Sometimes not all metadata (highLevelThreshold) is included when reading xml from FEWS:

test.xml:

        <TimeSeries xmlns="http://www.wldelft.nl/fews/PI" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.wldelft.nl/fews/PI http://fews.wldelft.nl/schemas/version1.0/pi-schemas/pi_timeseries.xsd" version="1.26" xmlns:fs="http://www.wldelft.nl/fews/fs">
            <timeZone>1.0</timeZone>
            <series>
                <header>
                    <type>instantaneous</type>
                    <moduleInstanceId>pr.gw.merge</moduleInstanceId>
                    <locationId>GW000001</locationId>
                    <parameterId>GW.G</parameterId>
                    <qualifierId>filter1</qualifierId>
                    <timeStep unit="nonequidistant"/>
                    <startDate date="2020-04-16" time="14:00:00"/>
                    <endDate date="2020-04-17" time="08:00:00"/>
                    <missVal>NaN</missVal>
                    <stationName>statname</stationName>
                    <lat>52.0</lat>
                    <lon>5.40</lon>
                    <x>150000.0</x>
                    <y>454000.0</y>
                    <z>3.3</z>
                    <units>mNAP</units>
                    <thresholds>
                        <highLevelThreshold id="MV_LTID" name="Maaiveld" label="Maaiveld Peilbuis" value="3.3" groupId="GW_LT" groupName="GW Level Thresholds"></highLevelThreshold>
                        <highLevelThreshold id="BKB_LTID_1" name="Bovenkant Buis" label="Bovenkant peilbuis filter 1" value="3.779" groupId="GW_LT" groupName="GW Level Thresholds"></highLevelThreshold>
                    </thresholds>
                </header>
                <event date="2020-04-16" time="14:00:00" value="2.119" flag="0"/>
                <event date="2020-04-16" time="20:00:00" value="2.122" flag="0"/>
                <event date="2020-04-17" time="02:00:00" value="2.123" flag="0"/>
                <event date="2020-04-17" time="08:00:00" value="2.121" flag="0"/>
            </series>
        </TimeSeries>

This:

xmlTree = ET.parse("test.xml").getroot()
for elem in xmlTree.iter():
    print(elem.tag)

gives:

{http://www.wldelft.nl/fews/PI}TimeSeries
{http://www.wldelft.nl/fews/PI}timeZone
{http://www.wldelft.nl/fews/PI}series
{http://www.wldelft.nl/fews/PI}header
{http://www.wldelft.nl/fews/PI}type
{http://www.wldelft.nl/fews/PI}moduleInstanceId
{http://www.wldelft.nl/fews/PI}locationId
{http://www.wldelft.nl/fews/PI}parameterId
{http://www.wldelft.nl/fews/PI}qualifierId
{http://www.wldelft.nl/fews/PI}timeStep
{http://www.wldelft.nl/fews/PI}startDate
{http://www.wldelft.nl/fews/PI}endDate
{http://www.wldelft.nl/fews/PI}missVal
{http://www.wldelft.nl/fews/PI}stationName
{http://www.wldelft.nl/fews/PI}lat
{http://www.wldelft.nl/fews/PI}lon
{http://www.wldelft.nl/fews/PI}x
{http://www.wldelft.nl/fews/PI}y
{http://www.wldelft.nl/fews/PI}z
{http://www.wldelft.nl/fews/PI}units
{http://www.wldelft.nl/fews/PI}thresholds
{http://www.wldelft.nl/fews/PI}highLevelThreshold
{http://www.wldelft.nl/fews/PI}highLevelThreshold
{http://www.wldelft.nl/fews/PI}event
{http://www.wldelft.nl/fews/PI}event
{http://www.wldelft.nl/fews/PI}event
{http://www.wldelft.nl/fews/PI}event

And this :

for f in xmlTree.iter("{http://www.wldelft.nl/fews/PI}highLevelThreshold"):
    print(f.tag)
    print(f.text)
    print(f.attrib)

gives :

{http://www.wldelft.nl/fews/PI}highLevelThreshold
None
{'id': 'MV_LTID', 'name': 'Maaiveld', 'label': 'Maaiveld Peilbuis', 'value': '3.3', 'groupId': 'GW_LT', 'groupName': 'GW Level Thresholds'}
{http://www.wldelft.nl/fews/PI}highLevelThreshold
None
{'id': 'BKB_LTID_1', 'name': 'Bovenkant Buis', 'label': 'Bovenkant peilbuis filter 1', 'value': '3.779', 'groupId': 'GW_LT', 'groupName': 'GW Level Thresholds'}

So the metadata is there somewhere but we have to fix how we extract it.