docs: public int getNumberOfSignaturesRequiredToSpend() {
          if (ScriptPattern.isSentToMultisig(this)) {
              // for N of M CHECKMULTISIG script we will need N signatures to spend
              ScriptChunk nChunk = chunks.get(0);
              return Script.decodeFromOpN(nChunk.opcode);
          } else if (ScriptPattern.isP2PKH(this) || ScriptPattern.isP2PK(this)) {
              // P2PKH and P2PK require single sig
              return 1;
          } else if (ScriptPattern.isP2SH(this)) {
              throw new IllegalStateException("For P2SH number of signatures depends on redeem script");
          } else {
              throw new IllegalStateException("Unsupported script type");
          }
      }