input: 
  from typing import List
  
  def print_number_triangle(n: int) -> str:
      """Print a triangle pattern of numbers up to n rows.
      Each row i contains numbers from 1 to i.
      
      >>> print_number_triangle(5)
      1
      12
      123
      1234
      12345
      >>> print_number_triangle(3)
      1
      12
      123
      """
  
output:     result = ""
      for i in range(1, n + 1):
          result += ''.join(str(j) for j in range(1, i + 1)) + "\n"
      return result