'Creates and saves a new item in a course.
Returns the newly created item.
Args:
user_id: ID of the user creating and saving the xmodule
course_key: A :class:`~opaque_keys.edx.CourseKey` identifying which course to create
this item in
block_type: The typo of block to create
block_id: a unique identifier for the new item. If not supplied,
a new identifier will be generated
fields (dict): A dictionary specifying initial values for some or all fields
in the newly created block'

@strip_key
@prepare_asides
def create_item(self, user_id, course_key, block_type, block_id=None, fields=None, **kwargs):

    modulestore = self._verify_modulestore_support(course_key, 'create_item')
    return modulestore.create_item(user_id, course_key, block_type, block_id=block_id, fields=fields, **kwargs)
