code: public String getVarNameForFieldAndFunction(DifferentialFunction function, String fieldName) {
          return fieldVariableResolutionMapping.get(function.getOwnName(), fieldName);
      }
docs: Get the variable name to use
  for resolving a given field
  for a given function during import time.
  This method is u sed during {@link DifferentialFunction#resolvePropertiesFromSameDiffBeforeExecution()}
  
  @param function  the function to get the variable name for
  @param fieldName the field name to resolve for
  @return the resolve variable name if any