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

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

        return $this;
    }
public function addField ( string $ field , string $ value ) : self { $ this -> fields [ $ field ] = $ value ; return $ this ; }
Add a field to this filter, such as 'title'.

@param string $field The field to filter on.
@param string $value The value to filter by.

@return self Fluent return.
Add a field to this filter such as title .