title: If no conditions are met, how do I raise a value error with np.select?
body: <p>Working with human labeled data, I have four cases that cover correct behavior, but it is possible for annotators to miss the need to provide a value. When this happens, I want the program to raise an error.</p>
  <pre><code>    #selects the final variation based on presence of other accepted variations
          dataframe[audit_cols[&quot;final_variation&quot;]] = np.select(
              #conditions
              [
                  dataframe[audit_cols[&quot;validation_step_new_variation&quot;]] != None,
                  dataframe[audit_cols[&quot;annotation_step_keyword&quot;]] != None, 
                  dataframe[audit_cols[&quot;keyword_feasible&quot;]] == &quot;NO&quot;, 
              ],
              #actions based on conditions
              [
                  dataframe[&quot;validation_step_new_variation&quot;]],
                  dataframe[&quot;annotation_step_keyword&quot;], 
                  #leaves blank if no variation seems feasible
                  &quot;&quot;,
              ],
      
              #raises error if no conditions are met
              default = raise ValueError(
                      &quot;No variation selected and the keyword has not been marked as unfeasible for row UID:&quot;,
                      dataframe[&quot;unique_ID&quot;],
                  )
      
          ) 
  </code></pre>
  <p>I'm open to any suggestions, and my primary question is &quot;how do I raise a value error if no cases are met?&quot; This is so future team members can see and address the eror.</p>