code: def upgrade():
      with op.batch_alter_table("clusters", schema=None) as batch_op:
          batch_op.alter_column(
              "broker_endpoint",
              existing_type=sa.VARCHAR(length=256),
              type_=sa.String(length=255),
              existing_nullable=True,
          )
          batch_op.alter_column(
              "broker_host",
              existing_type=sa.VARCHAR(length=256),
              type_=sa.String(length=255),
              existing_nullable=True,
          )
          batch_op.alter_column(
              "coordinator_endpoint",
              existing_type=sa.VARCHAR(length=256),
              type_=sa.String(length=255),
              existing_nullable=True,
          )
          batch_op.alter_column(
              "coordinator_host",
              existing_type=sa.VARCHAR(length=256),
              type_=sa.String(length=255),
              existing_nullable=True,
          )
  
      with op.batch_alter_table("columns", schema=None) as batch_op:
          batch_op.alter_column(
              "column_name",
              existing_type=sa.VARCHAR(length=256),
              type_=sa.String(length=255),
              existing_nullable=True,
          )
  
      with op.batch_alter_table("datasources", schema=None) as batch_op:
          batch_op.alter_column(
              "datasource_name",
              existing_type=sa.VARCHAR(length=256),
              type_=sa.String(length=255),
              existing_nullable=True,
          )
  
      with op.batch_alter_table(
          "table_columns", schema=None
      ) as batch_op:
          batch_op.alter_column(
              "column_name",
              existing_type=sa.VARCHAR(length=256),
              type_=sa.String(length=255),
              existing_nullable=True,
          )
  
      with op.batch_alter_table("tables", schema=None) as batch_op:
          batch_op.alter_column(
              "schema",
              existing_type=sa.VARCHAR(length=256),
              type_=sa.String(length=255),
              existing_nullable=True,
          )
  
imports: import sqlalchemy
  from alembic import op
label_desc: Use image node_id 1 for calling a global function with example usage: upgrade() without return types