code: def _get_instance_repo(self, namespace):
          
          self._validate_namespace(namespace)
          if namespace not in self.instances:
              self.instances[namespace] = []
          return self.instances[namespace]
docs: Returns the instance repository for the specified CIM namespace
          within the mock repository. This is the original instance variable,
          so any modifications will change the mock repository.
  
          Validates that the namespace exists in the mock repository.
  
          If the instance repository does not contain the namespace yet, it is
          added.
  
          Parameters:
  
            namespace(:term:`string`): Namespace name. Must not be `None`.
  
          Returns:
  
            list of CIMInstance: Instance repository.
  
          Raises:
  
            :exc:`~pywbem.CIMError`: CIM_ERR_INVALID_NAMESPACE: Namespace does
              not exist.