input: Write a function to print the following pattern: 5 rows of increasing asterisks followed by 5 rows of decreasing asterisks. If the input number of rows is negative or zero, print an empty string.
  def print_pattern(num_rows):
      if num_rows <= 0:
          print("")
          return
      for i in range(num_rows):
          for j in range(i+1):
              print("*", end="")
          print("")
      for i in range(num_rows, 0, -1):
          for j in range(i):
              print("*", end="")
          print("")
  
  assert print_pattern(5)==None # Output: \n*\n**\n***\n****\n*****\n****\n***\n**\n*\n
  assert print_pattern(3)==None # Output: \n*\n**\n***\n**\n*\n
  assert print_pattern(0)==None # Output: \n
  assert print_pattern(-1)==None # Output: \n
output: def print_pattern(num_rows):
      if num_rows <= 0:
          print("")
          return
      for i in range(num_rows):
          for j in range(i+1):
              print("*", end="")
          print("")
      for i in range(num_rows, 0, -1):
          for j in range(i):
              print("*", end="")
          print("")