docs: def getbalance(self, **params):
          """Get Account Asset Balance
  
          API Type
          --------
          HTTP Private API
  
          Docs
          ----
          https://lightning.bitflyer.jp/docs?lang=en#get-account-asset-balance
          """
          if not all([self.api_key, self.api_secret]):
              raise AuthException()
  
          endpoint = "/v1/me/getbalance"
          return self.request(endpoint, params=params)