Message list object

read_bufr() can take a message list object as an input. It is particularly useful if we already have the BUFR data in another object/storage structure and we want to directly use it with pdbufr.

A message list object is sequence of messages, where a message must be a mutable mapping of str BUFR keys to values. Ideally, the message object should implement a context manager (__enter__ and __exit__) and also the is_coord method, which determines if a key is a BUFR coordinate descriptor. If any of these methods are not available read_bufr() will automatically create a wrapper object to provide default implementations. For details see MessageWrapper in pdbufr/bufr_structure.py.