Sum of component.duration.seconds for each component in components.
Example:
abjad> t = FixedDurationTuplet((2, 8), construct.scale(3))
abjad> tempo = Tempo([t])
abjad> tempo.indication = TempoIndication(Rational(1, 4), 48)
abjad> print t.format
\times 2/3 {
\tempo 4=48
c'8
d'8
e'8
%% tempo 4=48 ends here
}
abjad> durtools.sum_seconds(t[:])
Rational(5, 4)