docs: def part(z, s):
      r"""Get the real or imaginary part of a complex number."""
      if sage_included:
          if s == 1: return np.real(z)
          elif s == -1: return np.imag(z)
          elif s == 0:
              return z
      else:
          if s == 1: return z.real
          elif s == -1: return z.imag
          elif s == 0: return z