 <tr>
   <td style="text-align:left;"> controlling-column-types-1 </td>
   <td style="text-align:left;"> exercise </td>
   <td style="text-align:left;"> read_csv("
         a, b, c
         1, 2, 3") </td>
  </tr>
  <tr>
   <td style="text-align:left;"> controlling-column-types-2 </td>
   <td style="text-align:left;"> exercise </td>
   <td style="text-align:left;"> read_csv("
  logical,numeric,date,string
  TRUE,1,2021-01-15,abc
  false,4.5,2021-02-15,def
  T,Inf,2021-02-16,ghi
") </td>
  </