'Fetch pull_request #:number: from :owner:/:repository
:param str owner: (required), owner of the repository
:param str repository: (required), name of the repository
:param int number: (required), issue number
:return: :class:`~github.pulls.PullRequest`'

def pull_request(self, owner, repository, number):

    json = None
    if (int(number) > 0):
        url = self._build_url(u'repos', owner, repository, u'pulls', str(number))
        json = self._json(self._get(url), 200)
    return self._instance_or_null(PullRequest, json)
