Add `is_character` method for `Reference` node

[joewallwork]

Partially addresses #2717.

This PR merges one of two functions from the types module of PSyACC into PSyclone.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.86%. Comparing base (33ff7e8) to head (87c257b). Report is 16 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2753   +/-   ##
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  Coverage   99.86%   99.86%           
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  Files         354      354           
  Lines       48967    48973    +6     
=======================================
+ Hits        48903    48909    +6     
  Misses         64       64           

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[arporter]

Could I be a bit cheeky and request a fix for a docstring formatting error from a previous PR? Building the Ref. Guide now gives:

PSyclone/src/psyclone/psyir/nodes/assignment.py:docstring of psyclone.psyir.nodes.Assignment.is_literal_assignment:3: WARNING: Definition list ends without a blank line; unexpected unindent.

which is new!

[joewallwork]

Could I be a bit cheeky and request a fix for a docstring formatting error from a previous PR? Building the Ref. Guide now gives:

PSyclone/src/psyclone/psyir/nodes/assignment.py:docstring of psyclone.psyir.nodes.Assignment.is_literal_assignment:3: WARNING: Definition list ends without a blank line; unexpected unindent.

which is new!

Ah good spot. Apologies, should be fixed in f2952478fc01c8e8d78cad0544dc43efd562054a.

[sergisiso]

Ah good spot. Apologies, should be fixed in https://github.com/stfc/PSyclone/commit/f2952478fc01c8e8d78cad0544dc43efd562054a.

Ups, I missed this on my review. I think the issue comes from missing the starting colon in the :returns: and :rtype: tags. It is also wrong in the method above.

With this fixed I don't think the backslash is necessary.

[joewallwork]

Ups, I missed this on my review. I think the issue comes from missing the starting colon in the :returns: and :rtype: tags. It is also wrong in the method above.

With this fixed I don't think the backslash is necessary.

Oh okay, I had just copied the syntax from the method above it. Fixed for both methods in 2c783a787f0b8daacf14f385b75e1d74290e0f65.

[joewallwork]

This is ready to merge now @jwallwork23 . Note that I ended up changing the "raise Exception" to a "raise ValueError" to avoid the pylint "broad-exception-raised" issue.

I also built the multiple documentations to verify the docstring warnings are gone.

Great, thanks @sergisiso!