code: def _mysql_drop_constraint(
      element: DropConstraint, compiler: MySQLDDLCompiler, **kw
  ) -> str:
      """Redefine SQLAlchemy's drop constraint to
      raise errors for invalid constraint type."""
  
      constraint = element.element
      if isinstance(
          constraint,
          (
              schema.ForeignKeyConstraint,
              schema.PrimaryKeyConstraint,
              schema.UniqueConstraint,
          ),
      ):
          assert not kw
          return compiler.visit_drop_constraint(element)
      elif isinstance(constraint, schema.CheckConstraint):
          # note that SQLAlchemy as of 1.2 does not yet support
          # DROP CONSTRAINT for MySQL/MariaDB, so we implement fully
          # here.
          if _is_mariadb(compiler.dialect):
              return "ALTER TABLE %s DROP CONSTRAINT %s" % (
                  compiler.preparer.format_table(constraint.table),
                  compiler.preparer.format_constraint(constraint),
              )
          else:
              return "ALTER TABLE %s DROP CHECK %s" % (
                  compiler.preparer.format_table(constraint.table),
                  compiler.preparer.format_constraint(constraint),
              )
      else:
          raise NotImplementedError(
              "No generic 'DROP CONSTRAINT' in MySQL - "
              "please specify constraint type"
          )
  
imports: from __future__ import annotations
  import re
  from typing import Any
  from typing import Optional
  from typing import TYPE_CHECKING
  from typing import Union
  from sqlalchemy import schema
  from sqlalchemy import types
  from .base import alter_table
  from .base import AlterColumn
  from .base import ColumnDefault
  from .base import ColumnName
  from .base import ColumnNullable
  from .base import ColumnType
  from .base import format_column_name
  from .base import format_server_default
  from .impl import DefaultImpl
  from ..None import util
  from ..util import sqla_compat
  from ..util.sqla_compat import _is_mariadb
  from ..util.sqla_compat import _is_type_bound
  from ..util.sqla_compat import compiles
label_desc: Use image node_id 6 for calling a global function with example usage: _mysql_drop_constraint(element, compiler) and returns: compiler, unknown, unknown