code: def format_tsv_line(source, edge, target, value=None, metadata=None):
      
      return '{source}\t{edge}\t{target}\t{value}\t{metadata}'.format(
          source=source,
          edge=edge,
          target=target,
          value='{:.4f}'.format(value) if value is not None else '',
          metadata=metadata or ''
      ).rstrip(' \t')
docs: Render a single line for TSV file with data flow described
  
      :type source str
      :type edge str
      :type target str
      :type value float
      :type metadata str
      :rtype: str