Description:
GrabVariables[ aListOfPolynomialsOrRules ] returns the
variables found in the list of (noncommutative) expressions
or rules aListOfPolynomialsOrRules. It is similar to
the Mathematica command Variables[] which takes
as an argument a list of polynomials in commutative variables
or functions of variables.
For example,
GrabVariables[ { x**Inv[x]**x + Tp[Inv[x+a]],
3 + 4 Inv[a]**b**Inv[a] + x }]
returns
{ x, a, b }.
