compareMain (other) {
	    if (!(other instanceof SemVer)) {
	      other = new SemVer(other, this.options);
	    }

	    return (
	      compareIdentifiers(this.major, other.major) ||
	      compareIdentifiers(this.minor, other.minor) ||
	      compareIdentifiers(this.patch, other.patch)
	    )
	  }
Set the client certificate option for https request.

@param {Buffer | String} cert
@return {Request} for chaining
@api public