remove side effects from methods

[arik-shurygin]

this is part of a broader push to make methods more functionally pure. There are pieces of code like:

DynODE/src/dynode/abstract_parameters.py

Lines 493 to 510 in 3690865

	def load_cross_immunity_matrix(self) -> None:
	"""
	Loads the Crossimmunity matrix given the strain interactions matrix.
	Strain interactions matrix is a matrix of shape (num_strains, num_strains) representing the relative immune escape risk
	of those who are being challenged by a strain in dim 0 but have recovered from a strain in dim 1.
	Neither the strain interactions matrix nor the crossimmunity matrix take into account waning.
	Updates
	----------
	self.config.CROSSIMMUNITY_MATRIX:
	updates this matrix to shape (self.config.NUM_STRAINS, self.config.NUM_PREV_INF_HIST) containing the relative immune escape
	values for each challenging strain compared to each prior immune history in the model.
	"""
	self.config.CROSSIMMUNITY_MATRIX = (
	utils.strain_interaction_to_cross_immunity(
	self.config.NUM_STRAINS, self.config.STRAIN_INTERACTIONS
	)
	)

within the AbstractParameters class which update self but do not return anything. I think it would be more explicit and better practice to have these types of functions return the parameter in question. Should also be on the look out for any functions which silently change anything about self, these "unpure" functions are likely to create bugs in the future and are bad practice.