Problem in accessing python visa module vxi11.py using class

I am using python instrumentation module called vxi11 to access a volt-meter which is connected via GPIB to Ethernet.

I can access the device if i use the module vxi11 directly inside my main program such as shown bellow;

import vxi11
if __name__ == "__main__":


    ################# Accessing the instrument without Class ##################
    ip = "192.168.1.5"
    DVM_addr = 23
    DVM_NPLC = 60

    def Open_GPIB(ip,addr):
              #addr_str = "gpib0," + unicode(addr)
              addr_str = "gpib0," + "{}".format(addr)
              return vxi11.Instrument(ip,addr_str)

    DVM = Open_GPIB(ip,DVM_addr)
    DVM.write("END ON")
    NPLC = "NPLC " + "{}".format(DVM_NPLC)
    DVM.write(NPLC)

However when I try to use a class based approach it will result in the following error;

bash-4.2$ temp1.py 
Traceback (most recent call last):
  File "./temp1.py", line 49, in <module>
    dvm.write("END ON")
  File "/anaconda3/python3.7/site-packages/vxi11/vxi11.py", line 727, in write
    self.write_raw(str(message).encode(encoding))
  File "/anaconda3/python3.7/site-packages/vxi11/vxi11.py", line 635, in write_raw
    self.open()
  File "/anaconda3/python3.7/site-packages/vxi11/vxi11.py", line 601, in open
    raise Vxi11Exception(error, 'open')
vxi11.vxi11.Vxi11Exception: 3: Device not accessible [open]

Following is the code for my class based approach;

import vxi11
class bppscalib(object):

    def __init__(self):

        self.ip = "192.168.1.5"
        self.DVM_addr = 23
        self.DVM = 0

        self.DVM_NPLC = 60
        self.Cycles = 165
        self.Cycle_time = 1.0

    def Open_GPIB(self, ip, addr):

        addr_str = "gpib0" + "{}".format(addr)
        return vxi11.Instrument(ip,addr_str)

if __name__ == "__main__":

    ################## Accessing the instrument with Class ###################
    bppscalib = bppscalib()
    dvm = bppscalib.Open_GPIB(bppscalib.ip,23)
    dvm.write("END ON")
    NPLC = "NPLC " + "{}".format(bppscalib.DVM_NPLC)
    dvm.write(NPLC)

And following is the line 601 in vxi11 that python is pointing to;

    def open(self):
        "Open connection to VXI-11 device"
        if self.link is not None:
            return

        if self.client is None:
            self.client = CoreClient(self.host)

        self.client.sock.settimeout(self.timeout+1)
        error, link, abort_port, max_recv_size = self.client.create_link(
            self.client_id,
            0,
            self._lock_timeout_ms,
            self.name.encode("utf-8")
        )

        if error:
            raise Vxi11Exception(error, 'open')

        self.abort_port = abort_port

        self.link = link
        self.max_recv_size = min(max_recv_size, 1024*1024)

My guess is the way I am including the vxi11.py module inside my class is not correct, see line return vxi11.Instrument(ip,addr_str) in def Open_GPIB()?

or alternatively I may use pyVisa module but I dont know how to use it, my GPIB device is at port 23 and ip address is 192.168.1.5. If I were to use pyVisa, what will be the equivalent of;

def Open_GPIB(ip,addr):
              #addr_str = "gpib0," + unicode(addr)
              addr_str = "gpib0," + "{}".format(addr)
              return vxi11.Instrument(ip,addr_str)

and equivalent of DVM.write("END ON")

Thanks

I got it. A comma is missing in Open_GPIB() function in gpib0 it should be gpib0,

addr_str = "gpib0," + "{}".format(addr)