@styleset, @swash, @ornaments, @annotation, @stylistic and @character-variant end up with an extraneous space.

[pygy]

@font-feature-values Font One {
  @styleset{
    ident0: 2;
  }
  @swash{
    ident1: 2;
  }
  @ornaments{
    ident2: 2;
  }
  @annotation{
    ident3: 2;
  }
  @stylistic{
    ident4: 2;
  }
  @character-variant{
    ident5: 2;
  }
}

Becomes

{
  '@global': {
    '@font-feature-values Font One': {
      '@styleset ': {
        ident0: 2
      },
      '@swash ': {
        ident1: 2
      },
      '@ornaments ': {
        ident2: 2
      },
      '@annotation ': {
        ident3: 2
      },
      '@stylistic ': {
        ident4: 2
      },
      '@character-variant ': {
        ident5: 2
      }
    }
  }
}

Where '@styleset ' should be '@styleset', etc...