idempotency attribute incorrectly flagged as an anonymous object in linter

[h1alexbel]

Here is the EO snippet:

[] > foo
  [] +> tests-slice-foreign-literals
    eq. > @
      "hello, 大家!".slice
        7
        1
      "大"

The test will be parsed to this XMIR:

<o line="405" name="+tests-slice-foreign-literals" pos="2">
   <o base="ξ.xi🌵" line="405" pos="2"/>
   <o base=".eq" line="406" name="φ" pos="4">
      <o base=".slice" line="407" pos="18">
         <o base="Φ.org.eolang.string" line="407" pos="6">
            <o as="α0" base="Φ.org.eolang.bytes" line="407" pos="6">
               <o as="α0" line="407" pos="6">68-65-6C-6C-6F-2C-20-E5-A4-A7-E5-AE-B6-21</o>
            </o>
         </o>
         <o base="Φ.org.eolang.number" line="408" pos="8">
            <o as="α0" base="Φ.org.eolang.bytes" line="408" pos="8">
               <o as="α0" line="408" pos="8">40-1C-00-00-00-00-00-00</o>
            </o>
         </o>
         <o base="Φ.org.eolang.number" line="409" pos="8">
            <o as="α0" base="Φ.org.eolang.bytes" line="409" pos="8">
               <o as="α0" line="409" pos="8">3F-F0-00-00-00-00-00-00</o>
            </o>
         </o>
      </o>
      <o base="Φ.org.eolang.string" line="410" pos="6">
         <o as="α0" base="Φ.org.eolang.bytes" line="410" pos="6">
            <o as="α0" line="410" pos="6">E5-A4-A7</o>
         </o>
      </o>
   </o>
</o>

And lints will complain:

It is prohibited to have formations like "+tests-slice-foreign-literals" that contain anonymous objects inside (anonymous-objects-inside-formation (Single))

Here, object with @base="ξ.xi🌵" (idempotency attribute) is technically anonymous, however we should not complain about it, since we need it for special reasons.

Let's not complain about idempotency attributes.

[h1alexbel]

@yegor256 new bug

[maxonfjvipon]

@h1alexbel I don't get it, why do we have such a object inside formation? Explicitly it should be like this:

[] > foo
  $ > xi🌵
  [] +> tests-slice-foreign-literals
    $ > xi🌵
    eq. > @
      "hello, 大家!".slice
        7
        1
      "大"

in XMIR:

<o line="405" name="+tests-slice-foreign-literals" pos="2">
   <o base="ξ" name="xi🌵" line="405" pos="2"/>
   ...
</o>

[h1alexbel]

@maxonfjvipon indeed, we should fix it first

[0crat]

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