code: def match_msequence(self, tokens, item):
          
          series_type, head_matches, middle, _, last_matches = tokens
          self.add_check("_coconut.isinstance(" + item + ", _coconut.abc.Sequence)")
          self.add_check("_coconut.len(" + item + ") >= " + str(len(head_matches) + len(last_matches)))
          if middle != wildcard:
              if len(head_matches) and len(last_matches):
                  splice = "[" + str(len(head_matches)) + ":" + str(-len(last_matches)) + "]"
              elif len(head_matches):
                  splice = "[" + str(len(head_matches)) + ":]"
              elif len(last_matches):
                  splice = "[:" + str(-len(last_matches)) + "]"
              else:
                  splice = ""
              self.assign_to_series(middle, series_type, item + splice)
          self.match_all_in(head_matches, item)
          for i, match in enumerate(last_matches):
              self.match(match, item + "[" + str(i - len(last_matches)) + "]")
docs: Matches a middle sequence.