Credo.Code.Heredocs.replace_with_spaces

You're seeing just the function replace_with_spaces, go back to Credo.Code.Heredocs module for more information.
Link to this function

replace_with_spaces(source_file, replacement \\ " ", interpolation_replacement \\ " ", empty_line_replacement \\ "", filename \\ "nofilename")

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Replaces all characters inside heredocs with the equivalent amount of white-space.