code: def change_custom_host_var(self, host, varname, varvalue):
          
          if varname.upper() in host.customs:
              host.modified_attributes |= DICT_MODATTR["MODATTR_CUSTOM_VARIABLE"].value
              host.customs[varname.upper()] = varvalue
  
              self.send_an_element(host.get_update_status_brok())
docs: Change custom host variable
          Format of the line that triggers function call::
  
          CHANGE_CUSTOM_HOST_VAR;<host_name>;<varname>;<varvalue>
  
          :param host: host to edit
          :type host: alignak.objects.host.Host
          :param varname: variable name to change
          :type varname: str
          :param varvalue: variable new value
          :type varvalue: str
          :return: None