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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def price_query_filter(price_query_dict):
 """ Ensure that certain keys are available. - exchange - period """

    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