function validate( opts, options ) {
	if ( !isPlainObject( options ) ) {
		return new TypeError( format( 'invalid argument. Options argument must be an object. Value: `%s`.', options ) );
	}
	if ( hasOwnProp( options, 'iter' ) ) {
		opts.iter = options.iter;
		if ( !isNonNegativeInteger( options.iter ) ) {
			return new TypeError( 'invalid option. `%s` option must be a nonnegative integer. Option: `%s`.', 'iter', options.iter );
		}
	}
	if ( hasOwnProp( options, 'tol' ) ) {
		opts.tol = options.tol;
		if ( !isFinite( options.tol ) || options.tol <= 0.0 ) {
			return new TypeError( format( 'invalid option. `%s` option must be a positive finite number. Option: `%s`.', 'tol', options.tol ) );
		}
	}
	return null;
}
Validates function options.

@private
@param {Object} opts - destination object
@param {Options} options - function options
@param {NonNegativeInteger} [options.iter] - maximum number of iterations
@param {PositiveNumber} [options.tol] - tolerance at which to terminate further evaluation of the continued fraction
@returns {(Error|null)} null or an error object

@example
var opts = {};
var options = {
    'iter': 50
};
var err = validate( opts, options );
if ( err ) {
    throw err;
}