src/Collection.php
public function set(string $key, $value): self
    {
        if (! isset($this->props[$key])) {
            throw new \Exception('Cannot add new property from set. Use add()');
        }

        $this->props[$key] = $value;

        return $this;
    }
public function set(string $key, $value): self
    {
        if (! isset($this->props[$key])) {
            throw new \Exception('Cannot add new property from set. Use add()');
        }

        $this->props[$key] = $value;

        return $this;
    }
public function set ( string $ key , $ value ) : self { if ( ! isset ( $ this -> props [ $ key ] ) ) { throw new \ Exception ( 'Cannot add new property from set. Use add()' ) ; } $ this -> props [ $ key ] = $ value ; return $ this ; }
set value of certain key on property cannot add new property, use add instead

@param mixed $value
set value of certain key on property cannot add new property use add instead