code: def get_gene_associations(model):
      
  
      for reaction in model.reactions:
          assoc = None
          if reaction.genes is None:
              continue
          elif isinstance(reaction.genes, string_types):
              assoc = boolean.Expression(reaction.genes)
          else:
              variables = [boolean.Variable(g) for g in reaction.genes]
              assoc = boolean.Expression(boolean.And(*variables))
          yield reaction.id, assoc
docs: Create gene association for class :class:`.GeneDeletionStrategy`.
  
      Return a dict mapping reaction IDs to
      :class:`psamm.expression.boolean.Expression` objects,
      representing relationships between reactions and related genes. This helper
      function should be called when creating :class:`.GeneDeletionStrategy`
      objects.
  
      Args:
          model: :class:`psamm.datasource.native.NativeModel`.