docs: def _significand(self):
          """Return the significand of self, as a BigFloat.
  
          If self is a nonzero finite number, return a BigFloat m
          with the same precision as self, such that
  
            0.5 <= m < 1. and
            self = +/-m * 2**e
  
          for some exponent e.
  
          If self is zero, infinity or nan, return a copy of self with
          the sign set to 0.
  
          """
          m = self.copy()
          if self and is_finite(self):
              mpfr.mpfr_set_exp(m, 0)
          mpfr.mpfr_setsign(m, m, False, ROUND_TIES_TO_EVEN)
          return m