Avoid dimshuffle if expand_dims has empty axis

[ricardoV94]

A small eager optimization we can do, to avoid useless dimshuffles.

Just return a if not axis before dim_it.

pytensor/pytensor/tensor/basic.py

Lines 4187 to 4206 in a76172e

	def expand_dims(
	a: np.ndarray | TensorVariable, axis: tuple[int, ...]
	) -> TensorVariable:
	"""Expand the shape of an array.
	Insert a new axis that will appear at the `axis` position in the expanded
	array shape.
	"""
	a = as_tensor(a)
	if not isinstance(axis, tuple | list):
	axis = (axis,)
	out_ndim = len(axis) + a.ndim
	axis = np.core.numeric.normalize_axis_tuple(axis, out_ndim)
	dim_it = iter(range(a.ndim))
	pattern = ["x" if ax in axis else next(dim_it) for ax in range(out_ndim)]
	return a.dimshuffle(pattern)

Squeeze already does this:

pytensor/pytensor/tensor/extra_ops.py

Lines 591 to 593 in a76172e

	if not axis:
	# Nothing to do
	return _x