function makeMainPath(dir) {
      return Blockly.utils.svgPaths.line([
        Blockly.utils.svgPaths.point(-width, 0),
        Blockly.utils.svgPaths.point(0, dir * height),
        Blockly.utils.svgPaths.point(width, 0),
      ]);
    }
Since input and output connections share the same shape you can define
a function to generate the path for both.
@param {number} dir Multiplier for the vertical direction of the path (-1 or 1)
@returns {Object} SVGPath line for use with input and output connections.