old_contents: from __future__ import unicode_literals
  
  from ..base import Resource
  
  from .agency import Agency
  
  
  class Agent(Resource):
      _resource_name = 'agents'
      _is_listable = False
  
      _as_is_fields = [
          'id', 'href', 'role', 'first_name', 'last_name', 'email',
          'phone_numbers', 'username', 'active',
      ]
      _resource_fields = [('agency', Agency)]
  
new_contents: from __future__ import unicode_literals
  
  from ..base import BaseModel, Resource
  
  from .agency import Agency
  
  
  class AgentRole(BaseModel):
      _as_is_fields = ['id', 'name']
  
  
  class AgentPhoneNumber(BaseModel):
      _as_is_fields = ['number', 'type']
  
  
  class Agent(Resource):
      _resource_name = 'agents'
      _is_listable = False
  
      _as_is_fields = [
          'id',
          'href',
          'first_name',
          'last_name',
          'email',
          'username',
          'active',
      ]
      _model_fields = [
          ('role', AgentRole),
      ]
      _model_collection_fields = [
          ('phone_numbers', AgentPhoneNumber),
      ]
      _resource_fields = [('agency', Agency)]
  
subject: Update Agent to use BaseModel classes to...