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: enum_all_relations.m
    path of file: ./repos/BPL/forward_model
    
    the code of the file until where you have to start completion: function [list_R,list_score_type] = enum_all_relations(previous_strokes,lib)
    % enumerate all possible ways a new stroke
    % can relate to the previous strokes
    %
    % This instantiates the discrete parameters, but not the  
    % continuous ones like continuous position and attachment.
    %
    % Input
    %  previous_strokes: cell array of stroke objects
    %  

    
function [list_R,list_score_type] = enum_all_relations(previous_strokes,lib)
    % enumerate all possible ways a new stroke
    % can relate to the previous strokes
    %
    % This instantiates the discrete parameters, but not the  
    % continuous ones like continuous position and attachment.
    %
    % Input
    %  previous_strokes: cell array of stroke objects
    %  
    % Output
    %   list_R: cell array of possible relations
    %   list_score_type : [n x 1] cached scores from
    %           CPD.score_relation_type, where "nan" indicates 
    %           a failure to cache (only the "unihist" case)
    ncpt = lib.ncpt;
    nprev = length(previous_strokes);    
    list_R{1} = RelationIndepend