get_attributes_duvenaud Function

  function get_attributes_duvenaud(this) result(attributes)
    !! Get the attributes of the Duvenaud message passing layer (for ONNX export)
    !!
    !! Exports hyperparameters needed to reconstruct the layer architecture:
    !!   - num_time_steps: number of message passing iterations
    !!   - min_vertex_degree, max_vertex_degree: degree bucket range
    !!   - num_vertex_features: vertex feature dimensions per time step
    !!   - num_edge_features: edge feature dimensions per time step
    !!   - num_outputs: readout output dimension
    !!   - message_activation, readout_activation: activation function names
    implicit none

    ! Arguments
    class(duvenaud_msgpass_layer_type), intent(in) :: this
    !! Instance of the layer
    type(onnx_attribute_type), allocatable, dimension(:) :: attributes
    !! Attributes of the layer

    ! Local variables
    integer :: t
    !! Time-step index
    character(256) :: buffer
    !! Buffer for integer-to-string conversion

    allocate(attributes(7))

    write(buffer, '(I0)') this%num_time_steps
    attributes(1) = onnx_attribute_type( &
         name='num_time_steps', type='int', val=trim(buffer))

    write(buffer, '(I0)') this%min_vertex_degree
    attributes(2) = onnx_attribute_type( &
         name='min_vertex_degree', type='int', val=trim(buffer))

    write(buffer, '(I0)') this%max_vertex_degree
    attributes(3) = onnx_attribute_type( &
         name='max_vertex_degree', type='int', val=trim(buffer))

    buffer = ''
    do t = 0, this%num_time_steps
       if(t .eq. 0)then
          write(buffer, '(I0)') this%num_vertex_features(t)
       else
          write(buffer, '(A," ",I0)') trim(buffer), this%num_vertex_features(t)
       end if
    end do
    attributes(4) = onnx_attribute_type( &
         name='num_vertex_features', type='ints', val=trim(buffer))

    buffer = ''
    do t = 0, this%num_time_steps
       if(t .eq. 0)then
          write(buffer, '(I0)') this%num_edge_features(t)
       else
          write(buffer, '(A," ",I0)') trim(buffer), this%num_edge_features(t)
       end if
    end do
    attributes(5) = onnx_attribute_type( &
         name='num_edge_features', type='ints', val=trim(buffer))

    write(buffer, '(I0)') this%num_outputs
    attributes(6) = onnx_attribute_type( &
         name='num_outputs', type='int', val=trim(buffer))

    attributes(7) = onnx_attribute_type( &
         name='message_activation', type='string', &
         val=trim(this%activation%name))

  end function get_attributes_duvenaud