<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def set_foreign_key(self, parent_table, parent_column, child_table, child_column):
 """Create a Foreign Key constraint on a column from a table."""

        self.execute('ALTER TABLE {0} ADD FOREIGN KEY ({1}) REFERENCES {2}({3})'.format(parent_table, parent_column,
                                                                                        child_table, child_column))