code: def _check_plot_engine(engine):
      """
      Check the validity of the plot engine.
  
      Parameters
      ----------
      engine : str
          The value of the plot engine to check.
  
      Raises
      ------
      ValueError
          If `engine` is not 'plotly' or 'matplotlib'.
      """
      if engine not in ["plotly", "matplotlib"]:
          raise ValueError(
              "plot_engine should be either 'plotly' or 'matplotlib'."
          )
  
imports: import numpy
  import pandas
  import psutil
label_desc: Use image node_id 20 for calling a global function with example usage: _check_plot_engine(engine) without return types