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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 install(self, xmlpath):
 """Installs the repository at the specified XML path as an additional repo to monitor pull requests for. """

        #Before we can install it, we need to make sure that none of the existing
        #installed paths point to the same repo.
        from os import path
        fullpath = path.abspath(path.expanduser(xmlpath))
        if path.isfile(fullpath):
            repo = RepositorySettings(self, fullpath)
            if repo.name.lower() not in self.repositories:
                self.installed.append(fullpath)
                self._save_installed()
                self.archive[repo.name.lower()] = {}
                self._save_archive()
                
                self.repositories[repo.name.lower()] = repo
        else:
            warn("The file {} does not exist; install aborted.".format(fullpath))