def create_back_links(env):
if env.needs_workflow['<STR_LIT>']:<EOL><INDENT>return<EOL><DEDENT>needs = env.needs_all_needs<EOL>for key, need in needs.items():<EOL><INDENT>for link in need["<STR_LIT>"]:<EOL><INDENT>link_main = link.split('<STR_LIT:.>')[<NUM_LIT:0>]<EOL>try:<EOL><INDENT>link_part = link.split('<STR_LIT:.>')[<NUM_LIT:1>]<EOL><DEDENT>except IndexError:<EOL><INDENT>link_part = None<EOL><DEDENT>if link_main in needs:<EOL><INDENT>if key not in needs[link_main]["<STR_LIT>"]:<EOL><INDENT>needs[link_main]["<STR_LIT>"].append(key)<EOL><DEDENT>if link_part is not None:<EOL><INDENT>if link_part in needs[link_main]['<STR_LIT>']:<EOL><INDENT>if '<STR_LIT>' not in needs[link_main]['<STR_LIT>'][link_part].keys():<EOL><INDENT>needs[link_main]['<STR_LIT>'][link_part]['<STR_LIT>'] = []<EOL><DEDENT>needs[link_main]['<STR_LIT>'][link_part]['<STR_LIT>'].append(key)<EOL><DEDENT><DEDENT><DEDENT><DEDENT><DEDENT>env.needs_workflow['<STR_LIT>'] = True<EOL>
Create back-links in all found needs.
But do this only once, as all needs are already collected and this sorting is for all
needs and not only for the ones of the current document.

:param env: sphinx enviroment
:return: None