A numeric specifying how many <epiparameter> objects to print.
This argument is passed to head() for list printing. Default is NULL
and the number of elements to print is controlled by package options().
# entire databasedb <- epiparameter_db()
db
# a single diseasedb <- epiparameter_db(disease = "Ebola")
db
# a single epi parameterdb <- epiparameter_db(epi_name = "offspring distribution")
db