You are given a string, s, and an array of strings, word_dict, representing a dictionary. Your task is to add spaces to s to break it up into a sequence of valid words from word_dict. We are required to return an array of all possible sequences of words (sentences). The order in which the sentences are listed is not significant.

Note: The same dictionary word may be reused multiple times in the segmentation.

Constraints:

• $1 \leq$ s.length $\leq 20$

• $1 \leq$ word_dict.length $\leq 1000$

• $1 \leq$ word_dict[i].length $\leq 10$

• s and word_dict[i] consist of only lowercase English letters.

• All the strings of word_dict are unique.