code: def gettrace(self, burn=0, thin=1, chain=-1, slicing=None):
          
  
          # XXX: handle chain == None case properly
  
          if chain is None:
              chain = -1
          chain = self.db.chains[chain]
  
          arr = self.db._arrays[chain, self.name]
  
          if slicing is not None:
              burn, stop, thin = slicing.start, slicing.stop, slicing.step
  
          if slicing is None or stop is None:
              stop = arr.nrows
              return np.asarray(arr.read(start=burn, stop=stop, step=thin))
docs: Return the trace (last by default).
  
          :Parameters:
          burn : integer
            The number of transient steps to skip.
          thin : integer
            Keep one in thin.
          chain : integer
            The index of the chain to fetch. If None, return all chains. The
            default is to return the last chain.
          slicing : slice object
            A slice overriding burn and thin assignement.