input: Write a function to print the following output pattern. The pattern consists of numbers starting from 1 and increasing by 1 in each row, up to the row number. After each number, a newline should be printed to start a new row.
  assert print_pattern()
  The output of the above assertion should be:
  1
  12
  123
  1234
  12345
output: def print_pattern():
      for i in range(1, 6):
          for j in range(1, i + 1):
              print(j, end='')
          print()