code: def get_mrca_idx_from_tip_labels(self, names=None, wildcard=None, regex=None):
          
          if not any([names, wildcard, regex]):
              raise ToytreeError("at least one argument required")
          node = fuzzy_match_tipnames(
              self, names, wildcard, regex, True, False)
          return node.idx
docs: Returns the node idx label of the most recent common ancestor node 
          for the clade that includes the selected tips. Arguments can use fuzzy
          name matching: a list of tip names, wildcard selector, or regex string.