class_docstr: A class for managing a circuit plot.
docstr: Draw a swap point as a cross.
docstr_tok: ["Draw","a","swap","point","as","a","cross","."]
code: def swap_point(self, gate_idx, wire_idx):
      """Draw a swap point as a cross."""
      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)
  
imports: from __future__ import annotations
  from sympy.core.mul import Mul
  from sympy.external import import_module
  from sympy.physics.quantum.gate import Gate, OneQubitGate, CGate, CGateS
label_desc: Use image node_id 16 for calling the CircuitPlot obj's underlying member method code with example usage: obj.swap_point(gate_idx, wire_idx) without return types