--> --> -->
Traceback (most recent call last):
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 3858, in _HandleRequest
    self._Dispatch(dispatcher, self.rfile, outfile, env_dict)
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 3792, in _Dispatch
    base_env_dict=env_dict)
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 580, in Dispatch
    base_env_dict=base_env_dict)
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 2918, in Dispatch
    self._module_dict)
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 2822, in ExecuteCGI
    reset_modules = exec_script(handler_path, cgi_path, hook)
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 2702, in ExecuteOrImportScript
    exec module_code in script_module.__dict__
  File "/home/askhader/work/TheWilletRepo/Apps/Plugin/plugin.py", line 34, in <module>
    from Models.customer import Customer, get_or_create_customer, get_customer_by_request
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 1440, in Decorate
    return func(self, *args, **kwargs)
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 2360, in load_module
    return self.FindAndLoadModule(submodule, fullname, search_path)
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 1440, in Decorate
    return func(self, *args, **kwargs)
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 2249, in FindAndLoadModule
    description)
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 1440, in Decorate
    return func(self, *args, **kwargs)
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 2194, in LoadModuleRestricted
    description)
  File "/home/askhader/work/TheWilletRepo/Models/customer.py", line 33, in <module>
    from Models.seller import Seller
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 1440, in Decorate
    return func(self, *args, **kwargs)
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 2360, in load_module
    return self.FindAndLoadModule(submodule, fullname, search_path)
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 1440, in Decorate
    return func(self, *args, **kwargs)
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 2249, in FindAndLoadModule
    description)
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 1440, in Decorate
    return func(self, *args, **kwargs)
  File "/home/askhader/work/google_appengine/google/appengine/tools/dev_appserver.py", line 2194, in LoadModuleRestricted
    description)
  File "/home/askhader/work/TheWilletRepo/Models/seller.py", line 44, in <module>
    class Seller( Model ):
  File "/home/askhader/work/google_appengine/google/appengine/ext/db/__init__.py", line 499, in __init__
    _initialize_properties(cls, name, bases, dct)
  File "/home/askhader/work/google_appengine/google/appengine/ext/db/__init__.py", line 414, in _initialize_properties
    attr.__property_config__(model_class, attr_name)
  File "/home/askhader/work/google_appengine/google/appengine/ext/db/__init__.py", line 3354, in __property_config__
    self.collection_name))
DuplicatePropertyError: Class Seller already has property seller_set