def swap_point(self, gate_idx, wire_idx):
            x = self._gate_grid[gate_idx]
            y = self._wire_grid[wire_idx]
            d = self.swap_delta
            l1 = Line2D(
                (x - d, x + d),
                (y - d, y + d),
                color='k',
                lw=self.linewidth
            )
            l2 = Line2D(
                (x - d, x + d),
                (y + d, y - d),
                color='k',
                lw=self.linewidth
            )
            self._axes.add_line(l1)
            self._axes.add_line(l2)
Draw a swap point as a cross.
dataset/ETHPy150Open sympy/sympy/sympy/physics/quantum/circuitplot.py/CircuitPlot.swap_point