code: def warn_if_nans_exist(X):
      """Warn if nans exist in a numpy array."""
      null_count = count_rows_with_nans(X)
      total = len(X)
      percent = 100 * null_count / total
  
      if null_count > 0:
          warning_message = (
              "Warning! Found {} rows of {} ({:0.2f}%) with nan values. Only "
              "complete rows will be plotted.".format(
                  null_count, total, percent
              )
          )
          warnings.warn(warning_message, DataWarning)
  
imports: import numpy
  import warnings
  from yellowbrick.exceptions import DataWarning
label_desc: Use image node_id 3 for calling a global function with example usage: warn_if_nans_exist(X) without return types