classWriteableSerializerMethodField(serializers.Field):def__init__(self,write_serializer=None,method_name=None,**kwargs):assertwrite_serializerisnotNoneandisinstance(write_serializer,serializers.Field),'write_serializer must be a valid serializer field'self.write_serializer=write_serializerself.method_name=method_namesuper(WriteableSerializerMethodField,self).__init__(**kwargs)defbind(self,field_name,parent):# In order to enforce a consistent style, we error if a redundant# 'method_name' argument has been used. For example:# my_field = serializer.CharField(source='my_field')default_method_name='get_{field_name}'.format(field_name=field_name)assertself.method_name!=default_method_name, ("It is redundant to specify `%s` on SerializerMethodField '%s' in ""serializer '%s', because it is the same as the default method name. ""Remove the `method_name` argument."%            (self.method_name,field_name,parent.__class__.__name__)        )# The method name should default to `get_{field_name}`.ifself.method_nameisNone:self.method_name=default_method_namesuper(WriteableSerializerMethodField,self).bind(field_name,parent)defto_internal_value(self,data):returnself.write_serializer.to_internal_value(data)defto_representation(self,value):method=getattr(self.parent,self.method_name)returnmethod(value)