class Prawn::Table

def assert_proper_table_data(data)
  if data.nil? || data.empty?
    raise Prawn::Errors::EmptyTable,
      "data must be a non-empty, non-nil, two dimensional array " +
      "of cell-convertible objects"
  end
  unless data.all? { |e| Array === e }
    raise Prawn::Errors::InvalidTableData,
      "data must be a two dimensional array of cellable objects"
  end
end