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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 prepare_sorting_fields(self):
 """ Determine sorting direction and sorting field based on request query parameters and sorting options of self """

        if self.sorting_parameter_name in self.request.query_params:
            # Extract sorting parameter from query string
            self._sorting_fields = [
                _.strip() for _ in self.request.query_params.get(self.sorting_parameter_name).split(',')
            ]

        if self._sorting_fields:
            # Create a list of sorting parameters. Each parameter is a tuple: (field:str, descending:bool)
            self._sorting_fields = [
                (self.sorting_fields_map.get(field.lstrip('-'), field.lstrip('-')), field[0] == '-')
                for field in self._sorting_fields
            ]