Often I would like to see what fields are defined in a collection. Especially when doing maintenance in the shell.
something like
db.mycollection.getFields()
to return all defined fields in all docs of a collection
or
db.mycol.getFields(

)
get all fields from docs where Field2 is defined in the doc
or
db.mycol.findFields(

)
get all fields from docs where the docType Field is defined and contains the value of "orderitems"