code: func isMultiSig(pops []parsedOpcode) bool {
  	// The absolute minimum is 1 pubkey:
  	// OP_0/OP_1-16 <pubkey> OP_1 OP_CHECKMULTISIG
  	l := len(pops)
  	if l < 4 {
  		return false
  	}
  	if !isSmallInt(pops[0].opcode) {
  		return false
  	}
  	if !isSmallInt(pops[l-2].opcode) {
  		return false
  	}
  	if pops[l-1].opcode.value != OP_CHECKMULTISIG {
  		return false
  	}
  
  	// Verify the number of pubkeys specified matches the actual number
  	// of pubkeys provided.
  	if l-2-1 != asSmallInt(pops[l-2].opcode) {
  		return false
  	}
  
  	for _, pop := range pops[1 : l-2] {
  		// Valid pubkeys are either 33 or 65 bytes.
  		if len(pop.data) != 33 && len(pop.data) != 65 {
  			return false
  		}
  	}
  	return true
  }
docs: // isMultiSig returns true if the passed script is a multisig transaction, false
  // otherwise.