input: Write a function to rewrite the given Python code snippet by introducing list comprehensions. If the original code appends elements to a list based on a condition, rewrite it using a list comprehension. If the original code is already in list comprehension form, return the original code.
  assert rewrite_with_comprehension("""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]'
  assert rewrite_with_comprehension("odd_numbers = [x for x in range(1, 11) if x % 2 != 0]")=='odd_numbers = [x for x in range(1, 11) if x % 2 != 0]'
  assert rewrite_with_comprehension("multiples_of_three = []\nfor i in range(3, 31, 3): multiples_of_three.append(i)")=='multiples_of_three = [i for i in range(3, 31, 3)]'
  assert rewrite_with_comprehension("")==''
  assert rewrite_with_comprehension("# This is a comment block\nsum_of_squares = sum([i**2 for i in range(1, 101)])")=='# This is a comment block\nsum_of_squares = sum([i**2 for i in range(1, 101)])'
output: def rewrite_with_comprehension(code):
      if 'for' in code and 'in' in code and 'if' in code and '.append(' in code:
          lines = code.strip().split('\n')
          var_name = lines[0].split('=')[0].strip()
          for_line = lines[1]
          if_line = lines[2] if len(lines) > 2 else ''
          for_part = for_line.split('for')[1].split('in')[0].strip()
          in_part = for_line.split('in')[1].split(':')[0].strip()
          if_part = if_line.split('if')[1].strip() if if_line else ''
          if if_part:
              return f"{var_name} = [{for_part} for {for_part} in {in_part} if {if_part}]"
          else:
              return f"{var_name} = [{for_part} for {for_part} in {in_part}]"
      elif '[' in code and 'for' in code and 'in' in code and ']' in code:
          return code.strip()
      else:
          return code.strip()