code: def _prepare_tab_css(self, css_opts: TabChartGlobalOpts) -> str:
      result = ""
      if isinstance(css_opts, TabChartGlobalOpts):
          css_opts = css_opts.opts
      css_opts = utils.remove_key_with_none_value(css_opts)
  
      def _dict_to_str(opts: dict, key: str, css_selector: str) -> str:
          _inner_result = ""
          for k, v in opts.get(key, dict()).items():
              _inner_result += "{}:{}; ".format(k, v)
          return (
              f"{css_selector} " + "{ " + _inner_result + " }\n"
              if _inner_result != ""
              else ""
          )
  
      # .tab
      tab_base = _dict_to_str(
          opts=css_opts, key="base", css_selector=".tab"
      )
      result += tab_base if tab_base != "" else DEFAULT_TAB_CSS
      # .tab button
      tab_button_base = _dict_to_str(
          opts=css_opts, key="button_base", css_selector=".tab button"
      )
      result += (
          tab_button_base
          if tab_button_base != ""
          else DEFAULT_TAB_BUTTON_CSS
      )
      # .tab button:hover
      tab_button_hover = _dict_to_str(
          opts=css_opts,
          key="button_hover",
          css_selector=".tab button:hover",
      )
      result += (
          tab_button_hover
          if tab_button_hover != ""
          else DEFAULT_TAB_BUTTON_HOVER_CSS
      )
      # .tab button.active
      tab_button_active = _dict_to_str(
          opts=css_opts,
          key="button_active",
          css_selector=".tab button.active",
      )
      result += (
          tab_button_active
          if tab_button_active != ""
          else DEFAULT_TAB_BUTTON_ACTIVE_CSS
      )
      if ".chart-container" not in result:
          result += """
              .chart-container { display: block; }
  
              .chart-container:nth-child(n+2) { display: none; }
              """
      return result
  
file_path: pyecharts/pyecharts/charts/composite_charts/tab.py
imports: import uuid
  from jinja2 import Environment
  from ...None import types
  from ...commons import utils
  from ...globals import CurrentConfig, ThemeType
  from ...options.charts_options import TabChartGlobalOpts
  from ...render import engine
  from ..mixins import CompositeMixin
label_desc: Use image node_id 3 for calling the Tab obj's underlying member method code with example usage: obj._prepare_tab_css(css_opts) and returns: result, unknown