code: def fit(self, t, y, dy=1, presorted=False):
          
          self.t, self.y, self.dy = self._validate_inputs(t, y, dy, presorted)
          self._fit(self.t, self.y, self.dy)
          return self
docs: Fit the smoother
  
          Parameters
          ----------
          t : array_like
              time locations of the points to smooth
          y : array_like
              y locations of the points to smooth
          dy : array_like or float (default = 1)
              Errors in the y values
          presorted : bool (default = False)
              If True, then t is assumed to be sorted.
  
          Returns
          -------
          self : Smoother instance