介绍一下这道数独题的解题步骤---**Question Stem:** This image presents a Sudoku puzzle. The implicit question is to solve the puzzle by filling in the empty cells such that each column, each row, and each of the nine 3x3 subgrids contain all of the digits from 1 to 9 exactly once. **Chart/Diagram Description:** * **Type:** Sudoku Grid. * **Main Elements:** * The image displays a 9x9 grid, which is the standard layout for a Sudoku puzzle. * The grid is visually partitioned by thicker lines into nine 3x3 subgrids (also known as blocks or boxes). * Each cell within the grid is designed to hold a single digit (1-9). * Numerous cells are pre-filled with digits. The remaining cells are empty, to be filled according to Sudoku rules. **Table Content:** The initial state of the Sudoku grid is as follows, with empty cells represented by an underscore `_`: Row 1: `_`, `6`, `1`, `_`, `3`, `_`, `_`, `2`, `_` Row 2: `_`, `5`, `_`, `_`, `_`, `8`, `1`, `_`, `7` Row 3: `_`, `_`, `_`, `_`, `7`, `_`, `_`, `3`, `4` Row 4: `_`, `_`, `9`, `_`, `_`, `6`, `3`, `7`, `8` Row 5: `_`, `_`, `3`, `2`, `7`, `9`, `5`, `_`, `_` Row 6: `5`, `7`, `_`, `3`, `_`, `_`, `_`, `9`, `2` Row 7: `1`, `9`, `_`, `7`, `6`, `_`, `_`, `_`, `_` Row 8: `8`, `_`, `2`, `4`, `_`, `_`, `_`, `7`, `6` Row 9: `6`, `4`, `_`, `_`, `1`, `_`, `_`, `2`, `5`