def from_activerecord relation, *fields
        Daru::IO.from_activerecord relation, *fields
      end
Read a dataframe from AR::Relation

@param relation [ActiveRecord::Relation] An AR::Relation object from which data is loaded
@param fields [Array] Field names to be loaded (optional)

@return A dataframe containing the data loaded from the relation

USE:

# When Post model is defined as:
class Post < ActiveRecord::Base
scope :active, -> { where.not(published_at: nil) }
end

# You can load active posts into a dataframe by:
Daru::DataFrame.from_activerecord(Post.active, :title, :published_at)