Write an API that generates fancy sequences using the `append`, `addAll`, and `multAll` operations.

Implement the `Fancy` class:

- `Fancy()` Initializes the object with an empty sequence.
- `void append(val)` Appends an integer `val` to the end of the sequence.
- `void addAll(inc)` Increments all existing values in the sequence by an integer `inc`.
- `void multAll(m)` Multiplies all existing values in the sequence by an integer `m`.
- `int getIndex(idx)` Gets the current value at index `idx` (0-indexed) of the sequence modulo `109 + 7`. If the index is greater or equal than the length of the sequence, return `-1`.

Example 1:

    Input
    ["Fancy", "append", "addAll", "append", "multAll", "getIndex", "addAll", "append", "multAll", "getIndex", "getIndex", "getIndex"]
    [[], [2], [3], [7], [2], [0], [3], [10], [2], [0], [1], [2]]
    Output
    [null, null, null, null, null, 10, null, null, null, 26, 34, 20]

    Explanation
    Fancy fancy = new Fancy();
    fancy.append(2);   // fancy sequence: [2]
    fancy.addAll(3);   // fancy sequence: [2+3] -> [5]
    fancy.append(7);   // fancy sequence: [5, 7]
    fancy.multAll(2);  // fancy sequence: [5*2, 7*2] -> [10, 14]
    fancy.getIndex(0); // return 10
    fancy.addAll(3);   // fancy sequence: [10+3, 14+3] -> [13, 17]
    fancy.append(10);  // fancy sequence: [13, 17, 10]
    fancy.multAll(2);  // fancy sequence: [13*2, 17*2, 10*2] -> [26, 34, 20]
    fancy.getIndex(0); // return 26
    fancy.getIndex(1); // return 34
    fancy.getIndex(2); // return 20

Constraints:

- `1 <= val, inc, m <= 100`
- `0 <= idx <= 105`
- At most `105` calls total will be made to `append`, `addAll`, `multAll`, and `getIndex`.