def __set_element(self, key, value):
        '''
        Fast assignment of the i,j element in the matrix
            This function is unsafe:
                1. Does not check on the value of key it expects key to be a integer tuple (i,j)
                2. Does not check bounds
                3. Does not check the value type
        '''
        if value: # only store non-zeros
            self.__data[key] = value
        elif self.__data in key:
            del self.__data[key]
dataset/ETHPy150Open fredrik-johansson/mpmath/mpmath/matrices/matrices.py/_matrix.__set_element/swapped operands of `in`