code: func (v *Value) Number() (json.Number, error) {
  	var valid bool
  
  	// Check the type of this data
  	switch v.data.(type) {
  	case json.Number:
  		valid = true
  	}
  
  	if valid {
  		return v.data.(json.Number), nil
  	}
  
  	return "", ErrNotNumber
  }
docs: // Attempts to typecast the current value into a number.
  // Returns error if the current value is not a json number.
  // Example:
  //		ageNumber, err := ageValue.Number()