I'm having hard time in trying to subscribe to the OnVif pullpoint services in standard IP cameras.

The SOAP client I'm using is Zeep <https://python-zeep.readthedocs.io/en/master/index.html>

It seems that Zeep constructs erroneous xml data, but I could be wrong (thanks to my limited knowledge of SOAP). Let's see the example:

```
from zeep.client import Client, CachingClient, Settings
from zeep.wsse.username import UsernameToken
import zeep.helpers

import logging.config

# # Put Zeep into verbose mode
logging.config.dictConfig({
    'version': 1,
    'formatters': {
        'verbose': {
            'format': '%(name)s: %(message)s'
        }
    },
    'handlers': {
        'console': {
            'level': 'DEBUG',
            'class': 'logging.StreamHandler',
            'formatter': 'verbose',
        },
    },
    'loggers': {
        'zeep.transports': {
            'level': 'DEBUG',
            'propagate': True,
            'handlers': ['console'],
        },
    }
})

ip="192.168.0.134"; user="admin"; passwd="123456"; port=80 # My home cam 1.  Now you know its username and password.  :)

settings = Settings()
settings.strict = False
settings.xml_huge_tree = True

# # WSDL File
url = "https://www.onvif.org/ver10/events/wsdl/event.wsdl"

# # *** Events Service ***
xaddr = "http://"+ip+"/onvif/events_service"
print("creating a soap client with url = ", url)
zeep_client_events = CachingClient(wsdl=url, wsse=UsernameToken(user, passwd, use_digest=True), settings=settings)
print("soap client created")
print("binding to service")
ws_client_events = zeep_client_events.create_service("{http://www.onvif.org/ver10/events/wsdl}EventBinding", xaddr)
print("service OK")

# # *** PullPoint Service ***
xaddr = "http://"+ip+"/onvif/events_service"
print("creating a soap client with url = ", url)
zeep_client_pp = CachingClient(wsdl=url, wsse=UsernameToken(user, passwd, use_digest=True), settings=settings)
print("soap client created")
print("binding to service")
ws_client_pp = zeep_client_pp.create_service("{http://www.onvif.org/ver10/events/wsdl}PullPointSubscriptionBinding", xaddr)
print("service bound")

res = ws_client_events.CreatePullPointSubscription()

# # could see the namespaces like this:
# zeep_client_pp.namespaces

# # could create PullMessages' parameters like this:
# pm = zeep_client_pp.get_element("ns7:PullMessages")()

# So, this call never works
ws_client_pp.PullMessages(MessageLimit=1, Timeout="PT1S")

```

Depending on the camera, this always results in "Remote end closed connection without response" or otherwise, the server sends a message that the value is invalid.

When putting Zeep into verbose mode and inspecting the SOAP message body (confirmed this with Wireshark as well) it look like this:

```
<soap-env:Body>
    <ns0:PullMessages xmlns:ns0="http://www.onvif.org/ver10/events/wsdl">
        <ns0:Timeout>P%P</ns0:Timeout>
        <ns0:MessageLimit>1</ns0:MessageLimit>
    </ns0:PullMessages>
</soap-env:Body>

```

So it seems that the string "PT1S" doesn't make its way into the message body, but there persists that "P%P" instead !

How to convince Zeep to insert the correct time in place?

P. S. And please, don't tell me to use "python-onvif-zeep". Of course I did that first and then ended up with this question (the examples of "python-onvif-zeep" for pullpoint services don't work)