first_conduit.py

all_securities = Security.objects.filter(company=company).for_report().iterator()

class FlatData(object):
    pass

def add_issue_date((flat, mdl)):
    flat.issue_date = mdl.get_issue_date()
    return (flat, mdl)

def add_label((flat, mdl)):
    flat.name = mdl.get_label()
    return (flat, mdl)

flat_securities = (
  conduit(all_securities)
      ...
      .map(lambda security: (FlatData(), security))
      .map(
          compose(
              add_issue_date,
              add_label,
          )
      )
      .map(lambda (flat, security): flat)
      ...
)