refactor DiagramID

[kunyuan]

The current implementation of DiagramID duplicates with DIagPara.type.

DiagramID should have larger scope than DiagPara.type. To be more specific,

DiagPara.type --> Ver4, Ver3, Green, Interaction, Sigma, ...
DiagramID --> N-body Vertex/Green/connected-Green in momentum-time representation, spacetime-representation, ...

So it is probably better to call it Representation. An example is the following,

#generic Veretx function in KX representation
struct VerKX
    para::DiagPara #DiagPara don't need weightType
    spin::Vector{Int} #[Up, Up], [Up, Down], ...
    channel::Channel # particle-hole, particle-hole exchange, particle-particle, irreducible, and their counterterms
    extK::Vector{Vector{Float64}}
    extT::Vector{Int}
    order::Vector{Int}   #[2, 0, 1] means loop-order 2, and one derivative of the second type.
end

it should come with some help functions (for example, a function to check if the vertex is instant or not).

The Diagram struct should be defined as,

struct Diagram{W, ID<:DiagramId}
      hash::Int
      name::Symbol
      id::ID
      operator::Operator
      factor::W
      subdiagram::Vector{Diagram{W, ID}}

      weight::W

Need some help functions (for example, isbare(diag) = (length(diag.subdiagram)==0))

[kunyuan]

Not relevant anymore