Update v2 condition table targetValue validation

[dweindl]

After PEtab-dev/PEtab#645, any condition that is used as a first condition cannot refer to any symbols other then the parameters listed in the parameter table, or `time'.

Closes #424.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 77.77778% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.82%. Comparing base (de974ba) to head (4df1ecb).

Files with missing lines	Patch %	Lines
petab/v2/lint.py	76.92%	3 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #427      +/-   ##
==========================================
+ Coverage   74.81%   74.82%   +0.01%     
==========================================
  Files          62       62              
  Lines        6765     6792      +27     
  Branches     1195     1203       +8     
==========================================
+ Hits         5061     5082      +21     
- Misses       1252     1255       +3     
- Partials      452      455       +3     

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[dilpath]

Looks good 👍

[dilpath]

Unrelated: the docstring for add_experiment is currently missing that multiple conditions applied at a single timepoint are specified as a list inside args

libpetab-python/petab/v2/core.py

Lines 2100 to 2109 in 8795dbf

	def add_experiment(self, id_: str, *args):
	"""Add an experiment to the problem.
	If there are more than one experiment tables, the experiment
	is added to the last one.
	:param id_: The experiment ID.
	:param args: Timepoints and associated conditions:
	``time_1, condition_id_1, time_2, condition_id_2, ...``.
	"""