class Practice < ActiveRecord::Base
        has_many :doctors, -> { where removed_at: nil }
    end

    class Doctor < ActiveRecord::Base
        scope :with_all_doctors, -> {includes(:practice).where.not removed_at: nil}
        belongs_to :practice
    end

doctor = Doctor.find(id: params[:id]) #here we are fetching object hierarchy with only active doctors of practice (doctor.practice.doctors will give only active users)

doctor = Doctor.with_all_doctors.find(id: params[:id]) #here we need to fetch object hierarchy with all doctors of practice (doctor.practice.doctors will give both active and removed doctors)