function isBoolean(value) {
      return value === true || value === false ||
        value && typeof value == 'object' && toString.call(value) == boolClass || false;
    }
Checks if `value` is a boolean value.

@static
@memberOf _
@category Objects
@param {*} value The value to check.
@returns {boolean} Returns `true` if the `value` is a boolean value, else `false`.
@example

_.isBoolean(null);
// => false