public function addFilterBy(string $field, string $value): self
    {
        $this->filterBy[$field] = $value;

        return $this;
    }
public function addFilterBy(string $field, string $value): self
    {
        $this->filterBy[$field] = $value;

        return $this;
    }
public function addFilterBy ( string $ field , string $ value ) : self { $ this -> filterBy [ $ field ] = $ value ; return $ this ; }
Adds a field to the current filtering set.

@param string $field
@param string $value

@return self
Adds a field to the current filtering set .