def group_cc_emails(audit_ccs, assessment_ccs):
  """Returns grouped cc emails between audit and assessment.

  Args:
    audit_ccs: List of audit ccs
    assessment_ccs: List of assessment ccs

  Returns:
    Grouped list of ccs
  """
  audit_ccs = frozenset(audit_ccs)
  assessment_ccs = frozenset(assessment_ccs)
  grouped_ccs = list(audit_ccs.union(assessment_ccs))

  return grouped_ccs