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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 get_repo_config(self, repo='default'):
 """Retrieve configuration for a given repository. Args: repo (str):
 a repository "realm" (alias) or its URL Returns: RepositoryConfig: if there is configuration for that repository None: otherwise """

        for repo_config in self.repositories:
            if repo_config.name == repo or repo_config.url in RepositoryURL(repo):
                return repo_config

        return None