can't change the style of the timesignatures

[Stefan Thomas]

Dear community,
I don't understand, why this snippet doesn't work:
\version "2.12.2"

\layout {
        \context { \override VerticalAlignment #'max-stretch = #ly:align-interface::calc-max-stretch }
        \context { \Voice \remove Text_spanner_engraver } 
  \context {  \override TimeSignature #'style = #'( ) } %why doesn't this this work cerrectly?
\context { \RemoveEmptyStaffContext \override VerticalAxisGroup #'remove-first = ##t } 
}
\new Staff \relative c' { c4 d e f g1 }