code: def next(self, n=1):
          
          if isinstance(self.label, SymbolicLabelBase):
              next_label = self.space.next_basis_label_or_index(
                  self.label, n)
              return BasisKet(next_label, hs=self.space)
          else:
              try:
                  next_index = self.space.next_basis_label_or_index(
                      self.index, n)
                  return BasisKet(next_index, hs=self.space)
              except IndexError:
                  return ZeroKet
docs: Move up by `n` steps in the Hilbert space::
  
              >>> hs =  LocalSpace('tls', basis=('g', 'e'))
              >>> ascii(BasisKet('g', hs=hs).next())
              '|e>^(tls)'
              >>> ascii(BasisKet(0, hs=hs).next())
              '|e>^(tls)'
  
          We can also go multiple steps:
  
              >>> hs =  LocalSpace('ten', dimension=10)
              >>> ascii(BasisKet(0, hs=hs).next(2))
              '|2>^(ten)'
  
          An increment that leads out of the Hilbert space returns zero::
  
              >>> BasisKet(0, hs=hs).next(10)
              ZeroKet