      a     b c     d    
  <dbl> <int> <lgl> <chr>
1   1       1 TRUE  a    
2   2.5     2 FALSE b    
3  NA      NA NA    <NA> 
  e     f         
  <fct> <date>    
1 a     2015-12-10
2 b     2015-12-11
3 <NA>  NA        
  g                  
  <dttm>             
1 2015-12-09 10:51:35
2 2015-12-09 10:51:36
3 NA                 
  h         i         
  <list>    <list>    
1 <int [1]> <list [2]>
2 <int [1]> <list [1]>
3 <int [1]> <list [1]>
