code: def upgrade():
      bind = op.get_bind()
      if isinstance(bind.dialect, MySQLDialect):
          with op.batch_alter_table("table_schema") as batch_op:
              batch_op.alter_column(
                  "description",
                  existing_type=sa.Text,
                  type_=mysql.LONGTEXT,
              )
  
imports: import sqlalchemy
  from alembic import op
  from sqlalchemy.dialects import mysql
  from sqlalchemy.dialects.mysql.base import MySQLDialect
label_desc: Use image node_id 1 for calling a global function with example usage: upgrade() without return types