In one sentence, explain what's wrong with this Ruby code. Then write a fixed version.

```ruby
def multiply_by_two(x)
  return x * 2
```
system
ek vaakya main, samajhaayen ki is rubi code main kya galat he.phir ek nishchit sanskaran likhen.

`` `rubi
def multicly_by_two (x)
  X * 2 lauten
`` `
user
rubi ke tareekon ko ek `def` or` and` block ke bheetar sanlagn kiya gaya he, or yah code `and` kiward ko yaad kar rahaa he.yahan ek nishchit sanskaran he:

`` `rubi
def multicly_by_two (x)
  X * 2 lauten
ant
`` `
assistant
<|system|>
</s>
<|user|>
ek vaakya main, samajhaayen ki is rubi code main kya galat he.phir ek nishchit sanskaran likhen.

`` `rubi
def multicly_by_two (x)
  X * 2 lauten
`` `</s>
<|assistant|>
rubi ke tareekon ko ek `def` or` and` block ke bheetar sanlagn kiya gaya he, or yah code `and` kiward ko yaad kar rahaa he.yahan ek nishchit sanskaran he:

`` `rubi
def multicly_by_two (x)
  X * 2 lauten
ant
`` `</s>
