The purpose of the expand() function is to look for nested collections inside your collection and flatten them into a single list. This is useful when you need to start manipulating nested data structures, such as a matrix or a tree. There, you will often need to flatten the collection as a data preparation step, before you can extract useful insights from the values:
final matrix = [
[1, 0, 0],
[0, 0, -1],
[0, 1, 0],
];
final linear = matrix.expand<int>((row) => row);
In this example, every element in the matrix list is another list. The expand function will loop through every element, and if the function returns a collection, it will destructure that collection into a linear list of values.
