docs: def add(self, child):
          """
          Adds a typed child object to the model.
  
          @param child: Child object to be added.
          """
  
          if isinstance(child, Include):
              self.add_include(child)
          elif isinstance(child, Dimension):
              self.add_dimension(child)
          elif isinstance(child, Unit):
              self.add_unit(child)
          elif isinstance(child, ComponentType):
              self.add_component_type(child)
          elif isinstance(child, Component):
              self.add_component(child)
          elif isinstance(child, FatComponent):
              self.add_fat_component(child)
          elif isinstance(child, Constant):
              self.add_constant(child)
          else:
              raise ModelError('Unsupported child element')