tst1:= (b/4)*(a^{i} + a^{j} - a^{j} );

# The Redberry authors claim we cannot do the following:

def testRB():
    ex:= K_a (A^{a b} - A^{b a});
    rl:= K_c (A^{c d} - A^{d c}) -> F^{d};
    substitute(ex, rl)
    tst:= F^{b} - @(ex);
    assert(tst==0)

testRB()




ex:= C B A D;
order(ex, 'A, B, C, D', anticommuting=True)

ex:= A B C D;
sym(ex, 'A, B, D')

ex:=     


def test04():
    \diff{#}::PartialDerivative.
    obj6:= \diff{g^{\mu \kappa} * \diff{g_{\kappa \nu}}_{\rho}}_{\sigma};
    product_rule(_)
    tst6:= \diff{g^{\mu \kappa}}_{\sigma} * \diff{g_{\kappa \nu}}_{\rho}
        +g^{\mu \kappa} * \diff{g_{\kappa \nu}}_{\rho \sigma} - @(obj6);
    collect_terms(_);

test04()

ctest([1,2,3])
ex:=a+b+c+d;
keep_terms(_, [1,2,3])