How to use the alembic.op.drop_constraint function in alembic

def downgrade():
    op.drop_constraint(op.f('fk_requests_event_id_events'), 'requests', schema='events')

# Upgrade UserOldId
    count = conn.scalar(sa.select([sa.func.count('*')]).select_from(useroldid))
    progress = get_progressbar("Old ids", count)
    progress.start()
    items = conn.execute(sa.select([useroldid.c.userid]))
    for counter, item in enumerate(items):
        conn.execute(
            sa.update(useroldid)
            .where(useroldid.c.userid == item.userid)
            .values(uuid=buid2uuid(item.userid))
        )
        progress.update(counter)
    progress.finish()

    op.drop_constraint('useroldid_pkey', 'useroldid', type_='primary')
    op.drop_column('useroldid', 'userid')
    op.drop_constraint('useroldid_uuid_key', 'useroldid', type_='unique')
    op.alter_column('useroldid', 'uuid', new_column_name='id')
    op.create_primary_key('useroldid_pkey', 'useroldid', ['id'])

create_foreign_key('reporthashes_report_id_fkey', 'reporthashes', 'reports',
                       ['report_id'], ['id'], ondelete='CASCADE')

    drop_constraint('reporthistorydaily_report_id_fkey', 'reporthistorydaily', type_='foreignkey')
    create_foreign_key('reporthistorydaily_report_id_fkey', 'reporthistorydaily', 'reports',
                       ['report_id'], ['id'], ondelete='CASCADE')

    drop_constraint('reporthistorymonthly_report_id_fkey', 'reporthistorymonthly', type_='foreignkey')
    create_foreign_key('reporthistorymonthly_report_id_fkey', 'reporthistorymonthly', 'reports',
                       ['report_id'], ['id'], ondelete='CASCADE')

    drop_constraint('reporthistoryweekly_report_id_fkey', 'reporthistoryweekly', type_='foreignkey')
    create_foreign_key('reporthistoryweekly_report_id_fkey', 'reporthistoryweekly', 'reports',
                       ['report_id'], ['id'], ondelete='CASCADE')

    drop_constraint('reportmantis_report_id_fkey', 'reportmantis', type_='foreignkey')
    create_foreign_key('reportmantis_report_id_fkey', 'reportmantis', 'reports',
                       ['report_id'], ['id'], ondelete='CASCADE')

    drop_constraint('reportopsysreleases_report_id_fkey', 'reportopsysreleases', type_='foreignkey')
    create_foreign_key('reportopsysreleases_report_id_fkey', 'reportopsysreleases', 'reports',
                       ['report_id'], ['id'], ondelete='CASCADE')

    drop_constraint('reportpackages_report_id_fkey', 'reportpackages', type_='foreignkey')
    create_foreign_key('reportpackages_report_id_fkey', 'reportpackages', 'reports',
                       ['report_id'], ['id'], ondelete='CASCADE')

    drop_constraint('reportraw_report_id_fkey', 'reportraw', type_='foreignkey')
    create_foreign_key('reportraw_report_id_fkey', 'reportraw', 'reports',
                       ['report_id'], ['id'], ondelete='CASCADE')

    drop_constraint('reportreasons_report_id_fkey', 'reportreasons', type_='foreignkey')

create_foreign_key('reportbtthreads_backtrace_id_fkey', 'reportbtthreads', 'reportbacktraces',
                       ['backtrace_id'], ['id'])

    drop_constraint('reportbthashes_backtrace_id_fkey', 'reportbthashes', type_='foreignkey')
    create_foreign_key('reportbthashes_backtrace_id_fkey', 'reportbthashes', 'reportbacktraces',
                       ['backtrace_id'], ['id'])

    drop_constraint('reportbtframes_thread_id_fkey', 'reportbtframes', type_='foreignkey')
    create_foreign_key('reportbtframes_thread_id_fkey', 'reportbtframes', 'reportbtthreads',
                       ['thread_id'], ['id'])

    drop_constraint('reportbttaintflags_backtrace_id_fkey', 'reportbttaintflags', type_='foreignkey')
    create_foreign_key('reportbttaintflags_backtrace_id_fkey', 'reportbttaintflags', 'reportbacktraces',
                       ['backtrace_id'], ['id'])

    drop_constraint('reportbtkernelmodules_backtrace_id_fkey', 'reportbtkernelmodules', type_='foreignkey')
    create_foreign_key('reportbtkernelmodules_backtrace_id_fkey', 'reportbtkernelmodules', 'reportbacktraces',
                       ['backtrace_id'], ['id'])

    drop_constraint('reportbacktraces_report_id_fkey', 'reportbacktraces', type_='foreignkey')
    create_foreign_key('reportbacktraces_report_id_fkey', 'reportbacktraces', 'reports',
                       ['report_id'], ['id'])

def downgrade():
    op.drop_constraint(
        "accounts_gpgkey_user_id_fkey", "accounts_gpgkey", type_="foreignkey"
    )
    op.create_foreign_key(
        "accounts_gpgkey_user_id_fkey",
        "accounts_gpgkey",
        "accounts_user",
        ["user_id"],
        ["id"],
        initially="DEFERRED",
        deferrable=True,
    )

def upgrade():
    # ### commands auto generated by Alembic - please adjust! ###
    op.add_column('Users', sa.Column('email', sa.String(length=50), nullable=False))
    op.add_column('Users', sa.Column('first_name', sa.String(length=50), nullable=False))
    op.add_column('Users', sa.Column('last_name', sa.String(length=50), nullable=False))
    op.drop_constraint('Users_username_key', 'Users', type_='unique')
    op.create_unique_constraint(None, 'Users', ['email'])
    op.drop_column('Users', 'username')
    # ### end Alembic commands ###

def downgrade():
    context = op.get_context()

    if context.bind.dialect.name == 'mssql':
        op.drop_constraint('ck_ps_endpoints_dtls_fingerprint_sha_hash_values', 'ps_endpoints')
    op.drop_column('ps_endpoints', 'dtls_fingerprint')

    if context.bind.dialect.name == 'postgresql':
        enum = ENUM(*SHA_HASH_VALUES, name=SHA_HASH_NAME)
        enum.drop(op.get_bind(), checkfirst=False)

"""
    bind = op.get_bind()
    session = Session(bind=bind)


    # create table harbor_label
    HarborLabel.__table__.create(bind)

    # create table harbor_resource_label
    HarborResourceLabel.__table__.create(bind)

    # create user_group
    UserGroup.__table__.create(bind)

    # project member
    op.drop_constraint('project_member_ibfk_1', 'project_member', type_='foreignkey')
    op.drop_constraint('project_member_ibfk_2', 'project_member', type_='foreignkey')
    op.drop_constraint('project_member_ibfk_3', 'project_member', type_='foreignkey')
    op.drop_constraint('PRIMARY', 'project_member', type_='primary')
    op.drop_index('user_id', 'project_member')
    op.drop_index('role', 'project_member')
    op.execute('ALTER TABLE project_member ADD id INT PRIMARY KEY AUTO_INCREMENT;')
    op.alter_column('project_member', 'user_id', existing_type=sa.Integer, existing_nullable=False, new_column_name='entity_id')
    op.alter_column('project_member', 'creation_time', existing_type=mysql.TIMESTAMP, server_default = sa.text("CURRENT_TIMESTAMP"))
    op.alter_column('project_member', 'update_time', existing_type=mysql.TIMESTAMP, server_default=sa.text("CURRENT_TIMESTAMP"), onupdate=sa.text("CURRENT_TIMESTAMP"))
    op.add_column('project_member', sa.Column('entity_type', sa.String(1)))

    session.query(ProjectMember).update({
        ProjectMember.entity_type: 'u'
    })
    op.alter_column('project_member', 'entity_type', existing_type=sa.String(1), existing_nullable=True, nullable=False)

sa.Column('state', sa.Text(), nullable=False),
    sa.Column('block_number', sa.Numeric(), nullable=False),
    sa.Column('block_hash', sa.String(length=66), nullable=True),
    sa.PrimaryKeyConstraint('id', name=op.f('pk_block_task_meta'))
    )
    op.alter_column('logs', 'address',
               existing_type=sa.VARCHAR(length=42),
               nullable=False)
    op.drop_constraint('fk_logs_transaction_hash_transactions', 'logs', type_='foreignkey')
    op.drop_constraint('fk_logs_block_number_blocks', 'logs', type_='foreignkey')
    op.create_foreign_key(op.f('fk_logs_transaction_hash_transactions'), 'logs', 'transactions', ['transaction_hash'], ['transaction_hash'], ondelete='CASCADE')
    op.create_foreign_key(op.f('fk_logs_block_number_blocks'), 'logs', 'blocks', ['block_number'], ['block_number'], ondelete='CASCADE')
    op.drop_constraint('fk_meta_info_last_pushed_block_blocks', 'meta_info', type_='foreignkey')
    op.create_foreign_key(op.f('fk_meta_info_last_pushed_block_blocks'), 'meta_info', 'blocks', ['last_pushed_block'], ['block_number'], ondelete='CASCADE')
    op.drop_constraint('fk_receipts_transaction_hash_transactions', 'receipts', type_='foreignkey')
    op.drop_constraint('fk_receipts_block_number_blocks', 'receipts', type_='foreignkey')
    op.create_foreign_key(op.f('fk_receipts_transaction_hash_transactions'), 'receipts', 'transactions', ['transaction_hash'], ['transaction_hash'], ondelete='CASCADE')
    op.create_foreign_key(op.f('fk_receipts_block_number_blocks'), 'receipts', 'blocks', ['block_number'], ['block_number'], ondelete='CASCADE')
    op.alter_column('state_diff', 'address',
               existing_type=sa.VARCHAR(length=42),
               nullable=False)
    op.drop_constraint('fk_state_diff_block_number_blocks', 'state_diff', type_='foreignkey')
    op.drop_constraint('fk_state_diff_transaction_hash_transactions', 'state_diff', type_='foreignkey')
    op.create_foreign_key(op.f('fk_state_diff_block_number_blocks'), 'state_diff', 'blocks', ['block_number'], ['block_number'], ondelete='CASCADE')
    op.create_foreign_key(op.f('fk_state_diff_transaction_hash_transactions'), 'state_diff', 'transactions', ['transaction_hash'], ['transaction_hash'], ondelete='CASCADE')
    op.drop_constraint('fk_storage_address_state', 'storage', type_='foreignkey')
    op.create_foreign_key(op.f('fk_storage_address_state'), 'storage', 'state', ['address'], ['address'], ondelete='CASCADE')
    op.drop_constraint('fk_storage_diff_block_number_blocks', 'storage_diff', type_='foreignkey')
    op.drop_constraint('fk_storage_diff_transaction_hash_transactions', 'storage_diff', type_='foreignkey')
    op.drop_constraint('fk_storage_diff_state_diff_id_state_diff', 'storage_diff', type_='foreignkey')
    op.create_foreign_key(op.f('fk_storage_diff_block_number_blocks'), 'storage_diff', 'blocks', ['block_number'], ['block_number'], ondelete='CASCADE')
    op.create_foreign_key(op.f('fk_storage_diff_transaction_hash_transactions'), 'storage_diff', 'transactions', ['transaction_hash'], ['transaction_hash'], ondelete='CASCADE')

def downgrade():
    ### commands auto generated by Alembic - please adjust! ###
    op.drop_column(u'users', 'is_group_owner')
    op.drop_constraint(op.f('uq_locks_lock_id'), 'locks', type_='unique')
    op.add_column(u'blueprints', sa.Column('plugin', sa.VARCHAR(length=32), autoincrement=False, nullable=True))
    op.drop_constraint(op.f('fk_blueprints_group_id_groups'), 'blueprints', type_='foreignkey')
    op.drop_constraint(op.f('fk_blueprints_template_id_blueprint_templates'), 'blueprints', type_='foreignkey')
    op.create_foreign_key(u'fk_blueprints_plugin_plugins', 'blueprints', 'plugins', ['plugin'], ['id'])
    op.drop_column(u'blueprints', 'template_id')
    op.drop_column(u'blueprints', 'group_id')
    op.drop_table('groups_users')
    op.drop_table('groups_owners')
    op.drop_table('groups_banned_users')
    op.drop_table('blueprint_templates')
    op.drop_table('groups')
    ### end Alembic commands ###