code: def _validate_namespace(self, namespace):
          
          if namespace not in self.namespaces:
              raise CIMError(
                  CIM_ERR_INVALID_NAMESPACE,
                  _format("Namespace does not exist in mock repository: {0!A}",
                          namespace))
docs: Validate whether a CIM namespace exists in the mock repository.
  
          Parameters:
  
            namespace (:term:`string`):
              The name of the CIM namespace in the mock repository. Must not be
              `None`.
  
          Raises:
  
            :exc:`~pywbem.CIMError`: CIM_ERR_INVALID_NAMESPACE: Namespace does
              not exist.