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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 extern_project_multi(self, context_handle, val, field_str_ptr, field_str_len):
 """Given a Key for `obj`, and a field name, project the field as a list of Keys."""

    c = self._ffi.from_handle(context_handle)
    obj = c.from_value(val[0])
    field_name = self.to_py_str(field_str_ptr, field_str_len)

    return c.vals_buf(tuple(c.to_value(p) for p in getattr(obj, field_name)))