_toTex (options) {
      const parenthesis =
          (options && options.parenthesis) ? options.parenthesis : 'keep'
      const parens =
          calculateNecessaryParentheses(
            this, parenthesis, options && options.implicit)

      let str = this.start.toTex(options)
      if (parens.start) {
        str = `\\left(${str}\\right)`
      }

      if (this.step) {
        let step = this.step.toTex(options)
        if (parens.step) {
          step = `\\left(${step}\\right)`
        }
        str += ':' + step
      }

      let end = this.end.toTex(options)
      if (parens.end) {
        end = `\\left(${end}\\right)`
      }
      str += ':' + end

      return str
    }
Get LaTeX representation
@params {Object} options
@return {string} str