You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: fixsegmentation.m
    path of file: ./repos/malini/Codes/deconvolution - model/spm8/external/fieldtrip/utilities/private
    
    the code of the file until where you have to start completion: function segmentation = fixsegmentation(segmentation, fn, style)

% FIXSEGMENTATION is a helper function that ensures the segmentation to be internally
% consistent. It is used by ft_datatype_segmentation and ft_datatype_parcellation.

    
function segmentation = fixsegmentation(segmentation, fn, style)

% FIXSEGMENTATION is a helper function that ensures the segmentation to be internally
% consistent. It is used by ft_datatype_segmentation and ft_datatype_parcellation.
%
% % See also CONVERT_SEGMENTATIONSTYLE, DETERMINE_SEGMENTATIONSTYLE

switch style
  case 'indexed'
    
    for i=1:length(fn)
      indexval = unique(segmentation.(fn{i})(:));  % find the unique tissue types
      indexval = indexval(indexval~=0);            % these are the only ones that matter
      
      if any(indexval<0)
        error('an indexed representation cannot contain negative numbers');
      end