Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Season no. | Series no. | Title | Directed by | Written by | Original air date | Production code | U.S. Viewers (millions) |
| --- | --- | --- | --- | --- | --- | --- | --- |
| 1.0 | 156.0 | "Playing Dead" | Michael Smith | Antoinette Stella | April19,2009 | 8009.0 | 4.57 |
| 2.0 | 157.0 | " Rock Star " | Bill D'Elia | Ed Zuckerman | April26,2009 | 8008.0 | 4.10 |
| 3.0 | 158.0 | "Identity Crisis" | Michael Smith | Pamela Wechsler | May3,2009 | 8005.0 | 3.14 |
| 4.0 | 159.0 | "In Treatment" | Jean de Segonzac | Timothy J. Lea | May10,2009 | 8010.0 | 3.14 |
| 5.0 | 160.0 | " Faithfully " | Jean de Segonzac | Antoinette Stella | May17,2009 | 8001.0 | 3.70 |
| 6.0 | 161.0 | "Astoria Helen" | Norberto Barba | Timothy J. Lea | May31,2009 | 8004.0 | 3.97 |
| 7.0 | 162.0 | "Folie à Deux" | David Manson | Michael S. Chernuchin | June7,2009 | 8003.0 | 3.90 |
| 8.0 | 163.0 | " The Glory That Was... " | Norberto Barba | Robert Nathan | June14,2009 | 8002.0 | 4.14 |
| 10.0 | 165.0 | "Salome in Manhattan" "Salome" | Steve Shill | Andrew Lipsitz | June28,2009 | 8006.0 | N/A |
| 11.0 | 166.0 | "Lady's Man" | Ken Girotti | Michael S. Chernuchin | June28,2009 | 8011.0 | N/A |
| 12.0 | 167.0 | "Passion" | Jonathan Herron | Michael S. Chernuchin | July12,2009 | 8012.0 | 3.47 |
| 14.0 | 169.0 | " Major Case " | Chris Zalla | Andrew Lipsitz | July26,2009 | 8014.0 | 4.63 |
| 15.0 | 170.0 | "Alpha Dog" | Norberto Barba | Walon Green | August2,2009 | 8007.0 | 4.23 |
Question:
who are the writer of the series episode number 170?
Answer:
Walon Green