code: '''Endpoints  POST /v1/customers/:id/balance_transactions   GET /v1/customers/:id/balance_transactions/:id  POST /v1/customers/:id/balance_transactions/:id   GET /v1/customers/:id/balance_transactions
  '''
nl: Customer Balance TransactionEach customer has a balance value,
  which denotes a debit or credit that's automatically applied to their next invoice upon finalization.
  You may modify the value directly by using the update customer API,
  or by creating a Customer Balance Transaction, which increments or decrements the customer's balance by the specified amount.