copy(): Series {
    return new Series(this.values, {index: this.index, name: this.name});
  }
Return a new deep copy of the `Series`

pandas equivalent: [Series.copy](http://pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.copy.html)

@returns {Series}

@example
const ds = new Series([1, 2, 3], {name: 'Test 1'});
const ds2 = ds.copy();
ds2.index = [1, 2, 3];
ds.index   // [0, 1, 2];
ds2.index  // [1, 2, 3];