code: def btc_is_multisig(privkey_info, **blockchain_opts):
      
      try:
          jsonschema.validate(privkey_info, PRIVKEY_MULTISIG_SCHEMA)
          return not privkey_info.get('segwit', False)
      except ValidationError as e:
          return False
docs: Does the given private key info represent
      a multisig bundle?
  
      For Bitcoin, this is true for multisig p2sh (not p2sh-p2wsh)