code: def get_public_key(self):
          
          res = self.get_public_key_info()
          if 'error' in res:
              raise ValueError(res['error'])
  
          if res['type'] != 'singlesig':
              raise ValueError(res['error'])
  
          return res['public_keys'][0]
docs: Parse the scriptSig and extract the public key.
          Raises ValueError if this is a multisig-controlled subdomain.