[base/section] Always set section type

Section type should always be set and now is set
by default to type='n.s.'.
This behaviour is introduced to Section.__init__
and is changed in the base method 'create_section'
from type='undefined' to type='n.s.' to ensure
equal behaviour.

Author: mpsonntag

odml/base.py

@@ -654,14 +654,19 @@ def get_repository(self):
         """
         return self._repository
 
-    def create_section(self, name, type="undefined", oid=None):
+    def create_section(self, name, type="n.s.", oid=None):
         """
         Creates a new subsection that is a child of this section.
 
-        :param name: The name of the section to create.
-        :param type: The type of the section.
+        :param name: The name of the section to create. If the name is not
+                 provided, the uuid of the Property is assigned as its name.
+                 Section name is a required attribute.
+        :param type: String providing a grouping description for similar Sections.
+                     Section type is a required attribute and will be set to the string
+                     'n.s.' by default.
         :param oid: object id, UUID string as specified in RFC 4122. If no id
                     is provided, an id will be generated and assigned.
+
         :return: The new section.
         """
         from odml.section import BaseSection

odml/section.py

@@ -27,7 +27,10 @@ class BaseSection(base.Sectionable):
 
     :param name: string providing the name of the Section. If the name is not
                  provided, the uuid of the Property is assigned as its name.
+                 Section name is a required attribute.
     :param type: String providing a grouping description for similar Sections.
+                 Section type is a required attribute and will be set to the string
+                 'n.s.' by default.
     :param parent: the parent object of the new Section. If the object is not
                    an odml.Section or an odml.Document, a ValueError is raised.
     :param definition: String describing the definition of the Section.
@@ -49,7 +52,7 @@ class BaseSection(base.Sectionable):
 
     _format = fmt.Section
 
-    def __init__(self, name=None, type=None, parent=None,
+    def __init__(self, name=None, type="n.s.", parent=None,
                  definition=None, reference=None,
                  repository=None, link=None, include=None, oid=None):