code: def null_handler(k):
      """
      Key method for sorting nulls correctly.
      """
      if k is None:
          return NullOrder()
  
      return k
  
file_path: agate/agate/columns.py
imports: from agate.mapped_sequence import MappedSequence
  from agate.utils import NullOrder, memoize
label_desc: Use image node_id 1 for calling a global function with example usage: null_handler(k) and returns: k, NullOrder