<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def fit(self, t, y, dy=1, presorted=False):
 """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 """

        self.t, self.y, self.dy = self._validate_inputs(t, y, dy, presorted)
        self._fit(self.t, self.y, self.dy)
        return self