How to get partial expression from symbolic expression containing specific variable MAPLE?

Question

I have a symbolic expressions as below

y1 = (1/a)-(b/a^2)+x*a*b-x/b
y2 = a*b+a*x+b*sqrt(x)

now I need to get the partial expressions which

Answer 1

listOfTerms = op(expression);  # y1 or y2
numberOfSubExpressions=nops(expression); # for y1 or y2

requiredTerm = 0;

for i 1 to numberOfSubExpressions do 
    if has(listOfTerms [i], x) then # x is our required term
       requiredTerm := requiredTerm +listOfTerms [i] 
    end if 
end do

Above code does my requirement. But, if are there any bugs for special expressions please let me know. Because op function behaves differently when we have functions like(sin,cos Log ..etc)