tensor_forward.py

class Tensor:
    def __init__(self, data, _parents=(), _op=''):
        self.data = data
        self.grad = 0
        self._backward = lambda: None
        # A set that contains previous (parent) nodes that produced 
        # the current node with operation _op
        self._prev = set(_parents)
        self._op = _op

    def __add__(self, other):
        out = Tensor(self.data + other.data, (self, other), '+')
        def _backward():
            self.grad += out.grad
            other.grad += out.grad
        out._backward = _backward
        return out

    def __mul__(self, other):
        out = Tensor(self.data * other.data, (self, other), '*')
        def _backward():
            self.grad += other.data * out.grad
            other.grad += self.data * out.grad
        out._backward = _backward
        return out

    def __pow__(self, other):
        out = Tensor(self.data**other, (self,), f'**{other}')
        def _backward():
            self.grad += (other * self.data**(other-1)) * out.grad
        out._backward = _backward
        return out

    def __neg__(self):
        return self * (-1)

    def __sub__(self, other):
        return self + (-other)
      
    ...