docstr: Test motif density
docstr_tok: ["Test","motif","density"]
code: def test_motif_density(self):
      "Test motif density"
      params = {
          "motif_name": "TAL1_known4",
          "seq_length": 1000,
          "num_seqs": 30,
          "min_counts": 2,
          "max_counts": 4,
          "GC_fraction": 0.4,
      }
      sequences, embed = dc.molnet.motif_density(**params)
      assert sequences.shape == (30,)
  
file_path: deepchem/deepchem/molnet/tests/test_dnasim.py
imports: import deepchem
  import unittest
label_desc: Use image node_id 4 for calling the TestDNASim obj's underlying member method code with example usage: obj.test_motif_density() without return types