The agent ID of the transmission source for the given condition
This function returns the agent ID of the transmission source for a given condition.
A transmissible condition within the model.
If the agent has been exposed to the given condition, this function returns the agent ID of the agent who transmitted the condition to the agent. If the agent was exposed through an importation, the function returns the ID of the meta-agent, -1.
If the agent has not been exposed to the condition, the function returns -1.
my_source_of_exposure = source(COND)