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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 main_pred_type(self, value):
 """set main predicate combination type :param value: (character) One of ``equals`` (``=``), ``and`` (``&``), ``or`` (``|``), ``lessThan`` (``<``), ``lessThanOrEquals`` (``<=``), ``greaterThan`` (``>``), ``greaterThanOrEquals`` (``>=``), ``in``, ``within``, ``not`` (``!``), ``like`` """

        if value not in operators:
            value = operator_lkup.get(value)
        if value:
            self._main_pred_type = value
            self.payload['predicate']['type'] = self._main_pred_type
        else:
            raise Exception("main predicate combiner not a valid operator")