def annotDataOrNone( gffRecordsByChrom, c ):
   """ return d which is either the list of GffRecords
   for a given chromosome, c, or return None.
   """
   if c not in gffRecordsByChrom:
      return None
   if gffRecordsByChrom[ c ] is None:
      return None
   if len( gffRecordsByChrom[ c ] ) < 1:
      return None
   return gffRecordsByChrom[ c ]