Create a placeholder for a named binary blob of data that is associated with this SR

Return value
	type	description
	blob	The reference of the blob, needed for populating its data
Parameters
name	type	description
session_id	session	valid session reference
sr	SR	The SR
name	string	The name associated with the blob
mime_type	string	The mime type for the data. Empty string translates to application/octet-stream
Errors
name	arguments	description

• Message has both a synchronous and asynchronous version
• This is a custom message