function isWeakMap(value) {
      return isObjectLike(value) && getTag(value) == weakMapTag;
    }
Checks if `value` is classified as a `WeakMap` object.

@static
@memberOf _
@since 4.3.0
@category Lang
@param {*} value The value to check.
@returns {boolean} Returns `true` if `value` is a weak map, else `false`.
@example

_.isWeakMap(new WeakMap);
// => true

_.isWeakMap(new Map);
// => false