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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_internals(model):
 """ Return non-boundary reactions and their metabolites. Boundary reactions are unbalanced by their nature. They are excluded here and only the metabolites of the others are considered. Parameters model : cobra.Model The metabolic model under investigation. """

    biomass = set(find_biomass_reaction(model))
    if len(biomass) == 0:
        LOGGER.warning("No biomass reaction detected. Consistency test results "
                       "are unreliable if one exists.")
    return set(model.reactions) - (set(model.boundary) | biomass)