Calling a service with parameters in a YAML file, passed as parameter in a launch file

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Hi. Here is my problem :

• I have two nodes A and B, where A launches a service which needs some parameters.
• Both are launched via a launch file where a YAML file is passed as a parameter to B with the 'rosparam' tag.
• The data represented in the YAML file correpond precisely to what the service in A needs as parameters.

Is there a way to call A from B with the content of the YAML without having to manually parse individually each values contained in the file (it's only composed of strings but the structure itself is pretty complex) ?

Thanks!