KeyTable.from_dataframe error

Hi, I was trying to incorporate an annotation table which is pyspark data frame:

annotation = KeyTable.from_dataframe(mytable,‘SampleID’)

got the error I don’t quite understand:
FatalError: MatchError: TimestampType (of class org.apache.spark.sql.types.TimestampType$)

Not all PySpark types are valid Hail types. You’ll need to make this DataFrame type a string first, I think.

This is also a bad error message, which is something we’ll want to fix in 0.2, but we’re not pushing patches like that to 0.1 anymore.