Given a binary string s (a string consisting only of '0' and '1's). Return the number of substrings with all characters 1's. Since the answer may be too large, return it modulo 10^9 + 7. Example 1: Input: s = "0110111" Output: 9 Explanation: There are 9 substring in total with only 1's characters. "1" -> 5 times. "11" -> 3 times. "111" -> 1 time. Example 2: Input: s = "101" Output: 2 Explanation: Substring "1" is shown 2 times in s. Example 3: Input: s = "111111" Output: 21 Explanation: Each substring contains only 1's characters. Example 4: Input: s = "000" Output: 0 Constraints: s[i] == '0' or s[i] == '1' 1 <= s.length <= 10^5