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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def create_pull(self, title, base, head, body=None):
 """Create a pull request of ``head`` onto ``base`` branch in this repo. :param str title: (required) :param str base: (required), e.g., 'master' :param str head: (required), e.g., 'username:branch' :param str body: (optional), markdown formatted description :returns: :class:`PullRequest <github3.pulls.PullRequest>` if successful, else None """

        data = {'title': title, 'body': body, 'base': base,
                'head': head}
        return self._create_pull(data)