code: def tx_for_tx_hash(self, tx_hash):
          
          url = "%s/rawtx/%s" % (self.url, b2h_rev(tx_hash))
          d = urlopen(url).read()
          j = json.loads(d.decode("utf8"))
          tx = Tx.from_hex(j.get("rawtx", ""))
          if tx.hash() == tx_hash:
              return tx
docs: Get a Tx by its hash.