def split_by_category(biom_cols, mapping, category_id):
columns = defaultdict(list)<EOL>for i, col in enumerate(biom_cols):<EOL><INDENT>columns[mapping[col['<STR_LIT:id>']][category_id]].append((i, col))<EOL><DEDENT>return columns<EOL>
Split up the column data in a biom table by mapping category value.