class_docstr: Positional encoding module.
  
  :param int n_units: embedding dim
  :param float dropout: dropout rate
  :param int length: maximum input length
docstr: Forward Positional Encoding.
docstr_tok: ["Forward","Positional","Encoding","."]
code: def forward(self, e):
      """Forward Positional Encoding."""
      length = e.shape[1]
      e = e * self.scale + self.xp.array(self.pe[:length])
      return F.dropout(e, self.dropout)
  
imports: import chainer
  import chainer.functions
  import numpy
label_desc: Use image node_id 2 for calling the PositionalEncoding obj's underlying member method code with example usage: obj.forward(e) and returns: F