code: func (sp *SourceProvider) GetSnippet(loc LocationRange) string {
  	var result bytes.Buffer
  	if loc.Begin.Line == 0 {
  		return ""
  	}
  	for i := loc.Begin.Line; i <= loc.End.Line; i++ {
  		inLineRange := trimToLine(loc, i)
  		for j := inLineRange.Begin.Column; j < inLineRange.End.Column; j++ {
  			result.WriteByte(loc.file.lines[i-1][j-1])
  		}
  		if i != loc.End.Line {
  			result.WriteByte('\n')
  		}
  	}
  	return result.String()
  }
docs: // GetSnippet returns a code snippet corresponding to loc.