docs: def set_linkage_method(self, method):
          """
          Sets the method to determine the distance between two clusters.
  
          :param method: The method to use. It can be one of ``'single'``,
              ``'complete'``, ``'average'`` or ``'uclus'``, or a callable. The
              callable should take two collections as parameters and return a
              distance value between both collections.
          """
          if method == 'single':
              self.linkage = single
          elif method == 'complete':
              self.linkage = complete
          elif method == 'average':
              self.linkage = average
          elif method == 'uclus':
              self.linkage = uclus
          elif hasattr(method, '__call__'):
              self.linkage = method
          else:
              raise ValueError('distance method must be one of single, '
                               'complete, average of uclus')