code: def start(self, labels=None):
          
  
          # Default label is self.dfltlbl
          if labels is None:
              labels = self.dfltlbl
          # If label is not a list or tuple, create a singleton list
          # containing it
          if not isinstance(labels, (list, tuple)):
              labels = [labels,]
          # Iterate over specified label(s)
          t = timer()
          for lbl in labels:
              # On first call to start for a label, set its accumulator to zero
              if lbl not in self.td:
                  self.td[lbl] = 0.0
                  self.t0[lbl] = None
              # Record the time at which start was called for this lbl if
              # it isn't already running
              if self.t0[lbl] is None:
                  self.t0[lbl] = t
docs: Start specified timer(s).
  
          Parameters
          ----------
          labels : string or list, optional (default None)
            Specify the label(s) of the timer(s) to be started. If it is
            ``None``, start the default timer with label specified by the
            ``dfltlbl`` parameter of :meth:`__init__`.