Checks if `value` is suitable for use as unique object key.

@private
@param {*} value The value to check.
@returns {boolean} Returns `true` if `value` is suitable, else `false`.
function isKeyable$2(value) {
	  var type = typeof value;
	  return (type == 'string' || type == 'number' || type == 'symbol' || type == 'boolean')
	    ? (value !== '__proto__')
	    : (value === null);
	}