Consider exposing the attributes of an Oligo's span as Oligo properties

[msto]

It may be convenient if Oligo implemented properties to expose corresponding attributes on the member Span, e.g.

@property
def start(self) -> int:
    """The oligo's start position on the target."""
    return self.span.start

An alternative solution would be to make Oligo inherit from or implement Span/Interval, so start/end/strand are attributes of Oligo, not one of its members.