class_docstr: Test other methods for manipulating/creating polynomial objects.
code: def test_deriv(self):
      other = self.p.deriv()
      assert_equal(other.symbol, "z")
  
imports: import pytest
  import numpy.polynomial
  from numpy.core import array
  from numpy.testing import assert_equal, assert_raises, assert_
label_desc: Use image node_id 6 for calling the TestExtraMethods obj's underlying member method code with example usage: obj.test_deriv() without return types