reset(a, b, c) {
    this.radius = Span.setSpanValue(a, b, c);
  }
Resets this initializer's parameters.
@param {number|Span} a - The radius value or the lower bound of the radius range.
@param {number} [b] - The upper bound of the radius range (if a is a number).
@param {boolean} [c] - Whether to use center-based calculation (if a and b are numbers).