'Calculates the standard deviation of the elements along the specified
axes.
Arguments:
a (Tensor): the Tensor on which to perform the operation
axis (int, optional): the dimension along which to compute.
If set to None, we will take std over all
dimensions.
out (Tensor, optional): where the result will be stored. If out is
None, only the op-tree will be returned.
partial (bool, optional): Not currently used.
keepdims (bool, optional): Keep the axes being computed over in the
output (with size 1), instead of
collapsing.  Defaults to True.
Returns:
OpTreeNode: the resulting op-tree'

@abc.abstractmethod
def std(self, a, axis=None, partial=None, out=None, keepdims=True):

    raise NotImplementedError()
