input: Write a function to print the following pattern: a triangle of asterisks that increases in size up to 5 rows and then decreases back to 1 row.
  assert print_pattern()==None
  
  for i in range(5):
      for j in range(i+1):
          print("*", end="")
      print("")
  
  for i in range(5, 0, -1):
      for j in range(i):
          print("*", end="")
      print("")
output: def print_pattern():
      for i in range(5):
          for j in range(i+1):
              print("*", end="")
          print("")
  
      for i in range(5, 0, -1):
          for j in range(i):
              print("*", end="")
          print("")