$1.$ Write a regular expression that replaces the cumbersome header lines of a FASTA formatted sequence file from GenBank $($e$.$g$.,$

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$>$gi$|63028387|$gb$|$AAY$27075\mathrm{.}1|$ Pax$6[$Oikopleura dioica$]$

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with the more elegant and tractable:

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$>\_$AAY$27075\_$Pax$6\_$Oikopleura$\_$dioica

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while retaining the sequences, themselves.

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Below are examples of four FASTA formatted protein sequence files for Pax$6$ to practice on$.$