code: def pm(self):
          
  
          resp = []
          data = {}
  
          # Send the command byte
          self.cnxn.xfer([0x32])
  
          # Wait 10 ms
          sleep(10e-3)
  
          # read the histogram
          for i in range(12):
              r = self.cnxn.xfer([0x00])[0]
              resp.append(r)
  
          # convert to real things and store in dictionary!
          data['PM1']     = self._calculate_float(resp[0:4])
          data['PM2.5']   = self._calculate_float(resp[4:8])
          data['PM10']    = self._calculate_float(resp[8:])
  
          sleep(0.1)
  
          return data
docs: Read the PM data and reset the histogram
  
          **NOTE: This method is supported by firmware v18+.**
  
          :rtype: dictionary
  
          :Example:
  
          >>> alpha.pm()
          {
              'PM1': 0.12,
              'PM2.5': 0.24,
              'PM10': 1.42
          }