### checking left hand side of an equation

Hi,
I'd like to check if the operation applied to an equation yields the solution as follow:
a=var('a')
eq= a+7==6

```
print eq.lhs()
LHS =(eq-7).lhs()
print LHS
LHS==a
a is a
LHS is a
```

I was waiting that the last line yields **True** or **False**. How can I check that LHS contains the variable **a**~~?~~?
edit `LHS is a`

yields **False**