Specify the position of a boundary within some coordinates.

Arguments: o position - The start position of the boundary o extension - The range to which the boundary can extend.

This allows dealing with a position like ((1.4)..100). This indicates that the start of the sequence is somewhere between 1 and 4. To represent that with this class we would set position as 1 and extension as 3.

__init__ (
        self,
        position,
        extension=0,
        )

__str__ ( self )