code: def _pivots(A_rref):
      """Return the pivots from the rref of A."""
      return tuple(sorted(map(min, A_rref.to_sdm().values())))
  
imports: from sympy import ZZ, QQ, ZZ_I, EX, Matrix, eye, zeros, symbols
  from sympy.polys.matrices import DM, DomainMatrix
  from sympy.polys.matrices.dense import ddm_irref_den, ddm_irref
  from sympy.polys.matrices.ddm import DDM
  from sympy.polys.matrices.sdm import SDM, sdm_irref, sdm_rref_den
  import pytest
label_desc: Use image node_id 2 for calling a global function with example usage: _pivots(A_rref) and returns: tuple