code: def price_query_filter(price_query_dict):
      
      if not isinstance(price_query_dict, dict):
          raise TypeError("dict_list is not a list. Please try again")
      required = ["period", "exchange"]
      pkeys = price_query_dict.keys()
      for r in required:
          if r not in pkeys:
              raise KeyError("An important key is not available {}".format(r))
      return True
docs: Ensure that certain keys are available.
              - exchange
              - period