def type
      defined?(@type) ? @type : :string
    end
The cell's data type.
Changing the type for a cell will recast the value into that type. If no type option is specified in the constructor, the type is
automatically determed.
@see Cell#cell_type_from_value
@return [Symbol] The type of data this cell's value is cast to.
@raise [ArgumentExeption] Cell.type must be one of [:date, time, :float, :integer, :string, :boolean]
@note
If the value provided cannot be cast into the type specified, type is changed to :string and the following logic is applied.
:string to :integer or :float, type conversions always return 0 or 0.0
:string, :integer, or :float to :time conversions always return the original value as a string and set the cells type to :string.
No support is currently implemented for parsing time strings.