code: def _read_state_variables(self):
          
          nodes = self.root.iterfind(
              './/ns:stateVariable', namespaces={'ns': self.namespace})
          for node in nodes:
              key = node.find(self.nodename('name')).text
              value = node.find(self.nodename('dataType')).text
              self.state_variables[key] = value
docs: Reads the stateVariable information from the xml-file.
          The information we like to extract are name and dataType so we
          can assign them later on to FritzActionArgument-instances.
          Returns a dictionary: key:value = name:dataType