List of variables and of expressions : lvar

lvar takes as argument an expression.
lvar returns a list of variable names and non-rationnal expressions such that it's argument is a rational fraction with respect to the variables and expressions of the list.
Input :

lvar(x*y*sin(x)^2)

Output :

[x,y,sin(x)]

Input :

lvar(x*y*sin(x)^2+ln(x)*cos(y))

Output :

[x,y,sin(x),ln(x),cos(y)]

Input :

lvar(y+x*sqrt(z)+y*sin(x))

Output :

[x,y,sqrt(z),sin(x)]