Reset the transfer info for a particular relation, or if none is given, for all relations.

def reset(self, relation_name=None):
    """Reset the transfer info for a particular relation, or if none is given, for all relations.
    """
    if relation_name is not None:
      self.data_access.delete("relations", dict(name=relation_name))
    else:
      self.data_access.delete("relations", "1=1")
    return self