code: def get(self, agentml, user=None, key=None):
          
          if not user or not key:
              return
  
          try:
              return user.get_var(key)
          except VarNotDefinedError:
              return
docs: Evaluate and return the current value of a user variable
          :param user: The active user object
          :type  user: agentml.User or None
  
          :param agentml: The active AgentML instance
          :type  agentml: AgentML
  
          :param key: The variables key
          :type  key: str
  
          :return: Current value of the user variable (or None if the variable has not been set)
          :rtype : str or None