def get_variables_from_monomial(monomial):
    """
    It is fed by a non-constant monomial like x*y*z and 
    returns a list consisting of given monomial's
    variables. which in this case are: ['x', 'y', 'z']
    """
    assert(not monomial.isdigit())
    temp = monomial.split('*')
    temp.sort()
    return temp