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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 find_best_server(filename):
 """Find the best server to open a notebook with."""

    servers = [si for si in notebookapp.list_running_servers()
               if filename.startswith(si['notebook_dir'])]
    try:
        return max(servers, key=lambda si: len(si['notebook_dir']))
    except ValueError:
        return None