Implementation changes

List of all from_etree methods

Class	Method signature	Accepts etree	Standart format	Note
Schema	def from_etree(schema_nodes, config: Config):	Yes	Yes
StructType	def from_etree(cls, type_node, config: Config):	Yes	No
EnumType	def from_etree(type_node, namespace, config: Config):	Yes	No
EntityType	def from_etree(cls, type_node, config: Config):	Yes	No	Should be
EntitySet	def from_etree(entity_set_node):	No	Yes
StructTypeProperty	def from_etree(entity_type_property_node):	No	Yes
NavigationTypeProperty	def from_etree(node):	No	Yes
EndRole	def from_etree(end_role_node):	No	Yes
ReferentialConstraint	def from_etree(referential_constraint_node, config: Config):	Yes	Yes
Association	def from_etree(association_node, config: Config):	Yes	Yes
AssociationSetEndRole	def from_etree(end_node):	No	Yes
AssociationSet	def from_etree(association_set_node, config: Config):	Yes	Yes
Annotation	def from_etree(target, annotation_node):	Yes	No
ExternalAnnotation	def from_etree(annotations_node):	Yes	Yes
ValueHelper	def from_etree(target, annotation_node):	Yes	No
ValueHelperParameter	def from_etree(value_help_parameter_node):	Yes	Yes
FunctionImport	def from_etree(function_import_node, config: Config):	Yes	Yes