docs: def regex_text(self) -> str:
          """
          Return regex text (yet to be compiled) for this drug.
          """
          if self._regex_text is None:
              possibilities = []  # type: List[str]
              for p in list(set(self.all_generics + self.alternatives)):
                  if self.add_preceding_word_boundary and not p.startswith(WB):
                      p = WB + p
                  if self.add_preceding_wildcards and not p.startswith(WILDCARD):
                      p = WILDCARD + p
                  if self.add_following_wildcards and not p.endswith(WILDCARD):
                      p = p + WILDCARD
                  possibilities.append(p)
              self._regex_text = "|".join("(?:" + x + ")" for x in possibilities)
          return self._regex_text