docstr: Coefficients should be modifiable 
docstr_tok: ["Coefficients","should","be","modifiable"]
code: def test_poly_coeffs_mutable(self):
      """Coefficients should be modifiable"""
      p = np.poly1d([1, 2, 3])
  
      p.coeffs += 1
      assert_equal(p.coeffs, [2, 3, 4])
  
      p.coeffs[2] += 10
      assert_equal(p.coeffs, [2, 3, 14])
  
      # this never used to be allowed - let's not add features to deprecated
      # APIs
      assert_raises(AttributeError, setattr, p, "coeffs", np.array(1))
  
imports: import numpy
  from numpy.testing import assert_, assert_equal, assert_array_equal, assert_almost_equal, assert_array_almost_equal, assert_raises, assert_allclose
  import pytest
label_desc: Use image node_id 18 for calling the TestPolynomial obj's underlying member method code with example usage: obj.test_poly_coeffs_mutable() without return types