class_docstr: stores a single scalar value and its gradient 
class_docstr_tok: ["stores","a","single","scalar","value","and","its","gradient"]
code: def __init__(self, data, _children=(), _op=""):
      self.data = data
      self.grad = 0
      # internal variables used for autograd graph construction
      self._backward = lambda: None
      self._prev = set(_children)
      self._op = _op
  
file_path: micrograd/micrograd/engine.py
label_desc: Use image node_id 1 to create a new Value object  with example: obj = Value(data, _children, _op)