parameters: (self, filter)
return_statement: return _resolved_filters.get(filter, None)
docstring: Returns the filter name for a filter function or `None` if there
          is no such filter.
docstring_summary: Returns the filter name for a filter function or `None` if there
          is no such filter.
docstring_tokens: Returns the filter name for a filter function or None if there is no such filter .
function: def get_filter_name(self, filter):
          """Returns the filter name for a filter function or `None` if there
          is no such filter.
          """
          if filter not in _resolved_filters:
              for library in libraries.values():
                  for key, value in library.filters.iteritems():
                      _resolved_filters[value] = key
          return _resolved_filters.get(filter, None)
function_tokens: def get_filter_name ( self , filter ) : if filter not in _resolved_filters : for library in libraries . values ( ) : for key , value in library . filters . iteritems ( ) : _resolved_filters [ value ] = key return _resolved_filters . get ( filter , None )