'Is X-Requested-With header present and equal to ``XMLHttpRequest``?
Note: this isn\'t set by every XMLHttpRequest request, it is
only set if you are using a Javascript library that sets it
(or you set the header yourself manually).  Currently
Prototype and jQuery are known to set this header.'

@property
def is_xhr(self):

    return (self.environ.get('HTTP_X_REQUESTED_WITH', '') == 'XMLHttpRequest')
