code: def replace_rdataset(self, replacement):
          
  
          self.delete_rdataset(replacement.rdclass, replacement.rdtype,
                               replacement.covers)
          self.rdatasets.append(replacement)
docs: Replace an rdataset.
  
          It is not an error if there is no rdataset matching I{replacement}.
  
          Ownership of the I{replacement} object is transferred to the node;
          in other words, this method does not store a copy of I{replacement}
          at the node, it stores I{replacement} itself.