def deregister_alternatives(self):
self._previous_registry = list(registry.items())<EOL>for key in list(registry.keys()):<EOL><INDENT>del registry[key]<EOL><DEDENT>registry['<STR_LIT>'] = Coverage<EOL>
Deregister any alternative metadata classes for the sake of testing. 
            This emulates the situation where there is only one metadata definition.