This method generates the GPS waypoints in a Loc
instance as a sequence of Gps instances.
Because these waypoints are stored in sequence in the ._gpsList attribute, we need only return an iterator
that visits the elements of that list, because an iterator is
also a generate that generates the values in the structure
over which it is iterating.
# - - - L o c . g e n G p s
def genGps(self):
"""Generate the waypoints in self.
"""
return iter(self._gpsList)