input: def rewrite_with_comprehensions(source_code: str) -> str:
      """ Rewrite the given Python code by introducing list comprehensions.
      >>> rewrite_with_comprehensions('''even_numbers = []
      ... for i in range(1,21):
      ...     if i % 2 == 0:
      ...         even_numbers.append(i)''')
      'even_numbers = [i for i in range(1, 21) if i % 2 == 0]'
      """
output:     lines = source_code.strip().split('\n')
      result = []
      i = 0
      while i < len(lines):
          if 'for' in lines[i] and 'in' in lines[i] and 'range' in lines[i]:
              for_line = lines[i].strip()
              if_line = lines[i+1].strip() if i+1 < len(lines) and 'if' in lines[i+1] else None
              append_line = lines[i+2].strip() if i+2 < len(lines) and '.append' in lines[i+2] else None
              if if_line and append_line:
                  var = for_line.split()[1]
                  range_expr = for_line.split('in')[-1].strip()
                  if_expr = if_line.split('if')[-1].strip()
                  append_expr = append_line.split('.append(')[-1][:-1]
                  result.append(f"{var} = [{append_expr} for {var} in {range_expr} if {if_expr}]")
                  i += 3
              else:
                  result.append(lines[i])
                  i += 1
          else:
              result.append(lines[i])
              i += 1
      return '\n'.join(result)