Event traces are passed as dataframes with at least two columns.
The first two columns contain event names and timestamps, respectively.
Names should be strings. Timestamps should be integers or strings, ideally,
but may be numeric.
Subsequent columns will be ignored by this function, for now.
Example dataframe events:
| name | timestamp | x | y |
-------------------------------
| foo | 123 | 2 | NA |
| bar | 987 | 3 | TRUE |