def find(self, sub, start=0, end=None):
        """Test if elements contain substring.

        Parameters
        ----------
        sub : str
        start : int, optional
            Index to start searching from.
        end : int, optional
            Index to stop searching from.

        Returns
        -------
        Series

        """
        check_type(sub, str)
        check_type(start, int)
        check_type(end, int)

        if end is not None and start >= end:
            raise ValueError('End must be greater than start')

        return Series(weld_str_find(self._data.values, sub, start, end),
                      self._data.index,
                      weld_to_numpy_dtype(WeldLong()),
                      self._data.name)
Test if elements contain substring.

        Parameters
        ----------
        sub : str
        start : int, optional
            Index to start searching from.
        end : int, optional
            Index to stop searching from.

        Returns
        -------
        Series