How to know when a date is incomplete and the missing parts

Is there a way to know when a date is incomplete. e.g "December 2015"

from dateparser import parse
parse(u'December 2015')  # default behavior
datetime.datetime(2015, 12, 16, 0, 0)
#is a way to do something like this
parse(u'December 2015', settings={'PREFER_DAY_OF_MONTH': 'incomplete'}) 
datetime.datetime(2015, 12, incomplete, 0, 0)
#the same with year or month

I need to parse data wich contains incomplete dates, in a nutshell i need the following to be done

from dateparser import parse
parse(u'December 2015', settings={'PREFER_DAY_OF_MONTH': 'incomplete'})  #it could be a string or other type
datetime.datetime(2015, 12, incomplete, 0, 0)

i´m sorry about my english, im self taught in it...

Start with the dateparser.parse entry point and the existing settings behavior for inputs such as "December 2015". Clarify how incomplete year, month, or day values should be represented, then define acceptance cases for detecting missing parts without relying on the default filled date. Done means the behavior and return type are specified and covered for the incomplete-date examples.