explain this `fibonacci.sum {| number | number * number }` in ruby

In the given code, fibonacci.sum is a method call where fibonacci is an instance of a class that has a sum method defined.

The sum method takes a block as an argument. In Ruby, a block is a piece of code that can be passed to a method and executed within that method's context. It is defined using { } or do ... end keywords.

In this particular example, the block {| number | number * number } is passed to the sum method. This block is used to define the logic for calculating the sum of the elements in the Fibonacci sequence.

The block takes an argument number and calculates the square of that number (number * number). The sum method then applies this block of code to each element in the Fibonacci sequence and returns the sum of the results.

So, the given code calculates the sum of the squares of the elements in the Fibonacci sequence.