TESTS:
- The trace inner product is commutative, bilinear, and satisfies
- the Jordan axiom:
+ The trace inner product is commutative, bilinear, and associative::
sage: set_random_seed()
sage: J = random_eja()
....: a*x.trace_inner_product(z) )
sage: actual == expected
True
- sage: # jordan axiom
+ sage: # associative
sage: (x*y).trace_inner_product(z) == y.trace_inner_product(x*z)
True