code: def sum(tensor, axis=None, keepdims=False):
      if axis is None:
          axis = tuple(range(tensor.ndim))
      return torch.sum(tensor, dim=axis, keepdim=keepdims)
  
imports: from packaging.version import Version
  import numpy
  from .core import Backend, backend_types, backend_basic_math, backend_array
label_desc: Use image node_id 15 for calling the PyTorchBackend obj's underlying member method code with example usage: obj.sum(tensor, axis, keepdims) and returns: torch