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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 delete_file(self, path, message, sha, branch=github.GithubObject.NotSet, committer=github.GithubObject.NotSet, author=github.GithubObject.NotSet):
 """This method deletes a file in a repository :calls: `DELETE /repos/:owner/:repo/contents/:path <https://developer.github.com/v3/repos/contents/#delete-a-file>`_ :param path: string, Required. The content path. :param message: string, Required. The commit message. :param sha: string, Required. The blob SHA of the file being replaced. :param branch: string. The branch name. Default: the repository’s default branch (usually master) :param committer: InputGitAuthor, (optional), if no information is given the authenticated user's information will be used. You must specify both a name and email. :param author: InputGitAuthor, (optional), if omitted this will be filled in with committer information. If passed, you must specify both a name and email. :rtype: { 'content': :class:`null <github.GithubObject.NotSet>`:, 'commit': :class:`Commit <github.Commit.Commit>`} """

        assert isinstance(path, (str, unicode)),                   \
            'path must be str/unicode object'
        assert isinstance(message, (str, unicode)),                \
            'message must be str/unicode object'
        assert isinstance(sha, (str, unicode)),                    \
            'sha must be a str/unicode object'
        assert branch is github.GithubObject.NotSet                \
            or isinstance(branch, (str, unicode)),                 \
            'branch must be a str/unicode object'
        assert author is github.GithubObject.NotSet                \
            or isinstance(author, github.InputGitAuthor),          \
            'author must be a github.InputGitAuthor object'
        assert committer is github.GithubObject.NotSet             \
            or isinstance(committer, github.InputGitAuthor),       \
            'committer must be a github.InputGitAuthor object'

        url_parameters = {'message': message, 'sha': sha}
        if branch is not github.GithubObject.NotSet:
            url_parameters['branch'] = branch
        if author is not github.GithubObject.NotSet:
            url_parameters["author"] = author._identity
        if committer is not github.GithubObject.NotSet:
            url_parameters["committer"] = committer._identity

        headers, data = self._requester.requestJsonAndCheck(
            "DELETE",
            self.url + "/contents/" + urllib.quote(path),
            input=url_parameters
        )

        return {'commit': github.Commit.Commit(self._requester, headers, data["commit"], completed=True),
                'content': github.GithubObject.NotSet}