code: def _approx_eq_(self, other: Any, atol: float) -> bool:
          
          if not isinstance(other, LinearDict):
              return NotImplemented
  
          all_vs = set(self.keys()) | set(other.keys())
          return all(abs(self[v] - other[v]) < atol for v in all_vs)
docs: Checks whether two linear combinations are approximately equal.