Implement the function logic to calculate the sum of account balance
To calculate the sum of account balance, the global function takes a value array of account balance as its parameter, and returns the calculated balance sum.
Note The global function does not take IColl data as its parameter. The specified ‘IColl.*.Balance’ is automatically transformed to an array of String values by using the instances’ ‘toString()’ method. So, it is required to ensure all the instances stored in ‘IColl.*.Balance’ can be transformed into valid String values via ‘toString()’ method. And meanwhile, the values can be transformed back to its original instance type.
