Feature request: direct access to source fields

When looking at a GenBank entry there often is interesting information in the "source" feature, which actually contains several subfields. From instance below one can see the "host" information:

I end up having to wrap the `gb_io.Record` class with another class to access this information. Also I end up constantly having to replace newlines with spaces.

class GenBankRecord:

def __init__(self, rec):
"""Get a record instance from gb_io"""
self.rec = rec

@functools.cached_property
def source(self):
"""Parse the first feature which is always 'source'"""
return next(iter(self.rec.features))

@functools.cached_property
def fields(self):
"""Get all subfields of source."""
return self.source.qualifiers.to_dict()

@functools.cached_property
def host(self):
if 'host' in self.fields:
return self.fields['host'][0].replace('\n', ' ')
return ''

It would be nice to just do `rec.host` no?