def _construct_layout(self):
        layout = QVBoxLayout()

        row = QToolBar()
        row.addWidget(header("Parameter Scenarios"))
        row.addAction(qicons.question, "About parameters scenarios",
                      self.explanation)
        layout.addWidget(row)
        layout.addWidget(horizontal_line())

        row = QHBoxLayout()
        row.addWidget(self.save_btn)
        row.addWidget(self.load_btn)
        row.addWidget(self.calculate_btn)
        row.addWidget(self.hide_group)
        row.addStretch(1)
        layout.addLayout(row)
        layout.addWidget(self.tbl)
        layout.addStretch(1)
        self.setLayout(layout)
    def _construct_layout(self):
        """ Construct the widget layout for the variable parameters tab
        """
        layout = QVBoxLayout()

        self.uncertainty_columns.setChecked(False)
        row = QToolBar()
        row.addWidget(header("Parameters "))
        row.addWidget(self.show_database_params)
        row.addWidget(self.uncertainty_columns)
        row.addAction(
            qicons.question, "About brightway parameters",
            self.explanation
        )
        layout.addWidget(row)
        layout.addWidget(horizontal_line())

        row = QHBoxLayout()
        row.addWidget(header("Project:"))
        row.addWidget(self.new_project_param)
        row.addStretch(1)
        layout.addLayout(row)
        layout.addWidget(self.project_table)

        row = QHBoxLayout()
        row.addWidget(self.database_header)
        row.addWidget(self.new_database_param)
        row.addStretch(1)
        layout.addLayout(row)
        layout.addWidget(self.database_table)

        row = QHBoxLayout()
        row.addWidget(header("Activity:"))
        row.addWidget(self.show_order)
        row.addStretch(1)
        layout.addLayout(row)
        layout.addWidget(self.activity_table)

        layout.addStretch(1)
        self.setLayout(layout)