Return a Budget with the associated budgetId.

    Args:
      client_customer_id: str Client Customer Id to which the budget belongs.
      budget_id: str id of the budget we want to examine.

    Returns:
      Budget A Budget data object.

def GetBudget(self, client_customer_id, budget_id):
    """Return a Budget with the associated budgetId.

    Args:
      client_customer_id: str Client Customer Id to which the budget belongs.
      budget_id: str id of the budget we want to examine.

    Returns:
      Budget A Budget data object.
    """
    self.client.SetClientCustomerId(client_customer_id)
    selector = {
        'fields': ['BudgetId', 'BudgetName', 'BudgetStatus', 'Amount',
                   'DeliveryMethod', 'BudgetReferenceCount',
                   'IsBudgetExplicitlyShared'],
        'predicates': [
            {
                'field': 'BudgetId',
                'operator': 'EQUALS',
                'values': [budget_id]
            }
        ]
    }
    budgets = self.client.GetService('BudgetService').get(selector)

    if int(budgets['totalNumEntries']) > 0:
      return budgets['entries'][0]
    else:
      return None