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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def list_entity_types(namespace, workspace):
 """List the entity types present in a workspace. Args: namespace (str):
 project to which workspace belongs workspace (str):
 Workspace name Swagger: https://api.firecloud.org/#!/Entities/getEntityTypes """

    headers = _fiss_agent_header({"Content-type":  "application/json"})
    uri = "workspaces/{0}/{1}/entities".format(namespace, workspace)
    return __get(uri, headers=headers)