def signatures_at filename, line, column
      position = Position.new(line, column)
      cursor = Source::Cursor.new(checkout(filename), position)
      api_map.clip(cursor).signify
    end
def signatures_at filename, line, column
      position = Position.new(line, column)
      cursor = Source::Cursor.new(checkout(filename), position)
      api_map.clip(cursor).signify
    end
Get signature suggestions for the method at the specified file and
 location.

 @param filename [String] The file to analyze
 @param line [Integer] The zero-based line number
 @param column [Integer] The zero-based column number
 @return [Array<Solargraph::Pin::Base>]
 @todo Take filename/position instead of filename/line/column