input: Write a python function to search for a target value in a 2D array.
  assert search([[1, 2, 3], [4, 5, 6], [7, 8, 9]], 5) == True
  assert search([[1, 2, 3], [4, 5, 6], [7, 8, 9]], 10) == False
  assert search([[], [], []], 1) == False
  assert search([[10, 20, 30], [40, 50, 60], [70, 80, 90]], 70) == True
output: def search(matrix, target):
      for row in matrix:
          if target in row:
              return True
      return False