`read_rainbow_wrl` version `5.65.2` support

[philipmassouh]

Is your feature request related to a problem? Please describe.
read_rainbow_wrl is unable to read rainbow file version 5.65.2(+?) because it assumes that metadata is stored in every slice:

pyart/pyart/aux_io/rainbow_wrl.py

Lines 286 to 292 in 99c78e2

	# range
	if not single_slice:
	# all sweeps have to have the same range resolution
	for i in range(nslices):
	slice_info = rbf["volume"]["scan"]["slice"][i]
	if slice_info["rangestep"] != common_slice_info["rangestep"]:
	raise ValueError("range resolution changes between sweeps")

In this case, 'rangestep' (among other things) is not in slice_info.

e.g.

>>> import wradlib as wr
>>> wr.__version__
'2.4.0'
>>> rbf = wr.io.read_rainbow(fp)
>>> rbf["volume"]["@version"]
'5.65.2'
>>> "rangestep" in rbf["volume"]["scan"]["slice"][0]
True
>>> "rangestep" in rbf["volume"]["scan"]["slice"][1]
False
>>> "rangestep" in rbf["volume"]["scan"]["slice"][2]
False
>>> len(rbf["volume"]["scan"]["slice"][0].keys())
88
>>> len(rbf["volume"]["scan"]["slice"][1].keys())
6
>>> len(rbf["volume"]["scan"]["slice"][2].keys())
6

Describe the solution you'd like
I think we can change the library to only check if it's available:

    # range
    if not single_slice:
        # all sweeps have to have the same range resolution
        for i in range(nslices):
            slice_info = rbf["volume"]["scan"]["slice"][i]
            if (
                "rangestep" in slice_info
                and slice_info["rangestep"] != common_slice_info["rangestep"]
            ):
                raise ValueError("range resolution changes between sweeps")

Describe alternatives you've considered
Given my use case, this function is my preferred way to parse rainbow files. I will open a PR if this change is acceptable. Thanks.

[zssherman]

@kmuehlbauer Apologies for the ping, but do we handle these situations in xradar?

[kmuehlbauer]

@zssherman I do not know by heart, so I would test it with xradar. This somehow rings a bell, but I'm really not sure.

[zssherman]

@kmuehlbauer No worries! Thanks for the response!

[zssherman]

Wanted to give an update, but after discussion, we are recommending users for the aux_io module to use xradar for reading files as we are depreciating some of the readers here.

An example of this is:

import xradar as xd

import pyart
from pyart.testing import get_test_data

# Locate the test data and read in using xradar
tree = xd.io.open_rainbow_datatree([filename])
# Give the tree Py-ART radar methods
radar = tree.pyart.to_radar()

# Plot the Reflectivity Field (corrected_reflectivity_horizontal)
display = pyart.graph.RadarMapDisplay(radar)
display.plot_ppi(
    "corrected_reflectivity_horizontal", cmap="ChaseSpectral", vmin=-20, vmax=70
)