parameters: (val, f, field_filter)
docstring: get CSV representation of fields used by _str_plot
      :returns: list of fields as a CSV string, ``str``
docstring_summary: get CSV representation of fields used by _str_plot
      :returns: list of fields as a CSV string, ``str``
docstring_tokens: get CSV representation of fields used by _str_plot : returns : list of fields as a CSV string str
function: def _str_plot_fields(val, f, field_filter):
      """
      get CSV representation of fields used by _str_plot
      :returns: list of fields as a CSV string, ``str``
      """
      s = _sub_str_plot_fields(val, f, field_filter)
      if s is not None:
          return "time,"+s
      else:
          return 'time,'
function_tokens: def _str_plot_fields ( val , f , field_filter ) : s = _sub_str_plot_fields ( val , f , field_filter ) if s is not None : return "time," + s else : return 'time,'