code: def remove_column(conn, table, column_name, schema=None):
      
      activity_table = get_activity_table(schema=schema)
      remove = sa.cast(column_name, sa.Text)
      query = (
          activity_table
          .update()
          .values(
              old_data=activity_table.c.old_data - remove,
              changed_data=activity_table.c.changed_data - remove,
          )
          .where(activity_table.c.table_name == table)
      )
      return conn.execute(query)
docs: Removes given `activity` jsonb data column key. This function is useful
      when you are doing schema changes that require removing a column.
  
      Let's say you've been using PostgreSQL-Audit for a while for a table called
      article. Now you want to remove one audited column called 'created_at' from
      this table.
  
      ::
  
          from alembic import op
          from postgresql_audit import remove_column
  
  
          def upgrade():
              op.remove_column('article', 'created_at')
              remove_column(op, 'article', 'created_at')
  
  
      :param conn:
          An object that is able to execute SQL (either SQLAlchemy Connection,
          Engine or Alembic Operations object)
      :param table:
          The table to remove the column from
      :param column_name:
          Name of the column to remove
      :param schema:
          Optional name of schema to use.